Liquid crystal display

ABSTRACT

A liquid crystal display is furnished with: a liquid crystal display element having a pair of substrates, to which alignment members are provided to their respective opposing surfaces, and a liquid crystal layer sandwiched by the pair of substrates; an alignment mechanism for providing at least two different director configurations simultaneously on different arbitrary regions used for display in the liquid crystal layer; and a reflection film provided to at least one of the different arbitrary regions showing different director configurations; wherein the different arbitrary regions showing different director configurations are used for a reflection display section for showing reflection display and a transmission display section for showing transmission display, respectively. Examples of the alignment mechanism include an alignment film to which the alignment treatment is applied in different orientations in the reflection display section and transmission display section, respectively, an insulation film having different film thicknesses in the reflection display section and transmission display section, and so forth.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of co-pending application Ser. No.12/427,449 filed Apr. 21, 2009, which is a Divisional of co-pendingapplication Ser. No. 12/051,776 filed on Mar. 19, 2008, which is adivisional of application Ser. No. 11/333,304 filed on Jan. 18, 2006,now U.S. Pat. No. 7,394,511 issued Jul. 1, 2008, which is a divisionalof application Ser. No. 10/774,625 filed on Feb. 10, 2004, now U.S. Pat.No. 7,050,132 issued May 23, 2006, which is a divisional of applicationSer. No. 10/177,149 filed on filed on Jun. 24, 2002, now U.S. Pat. No.6,900,863 B2 issued May 31, 2005, which is a divisional of applicationSer. No. 09/887,442 filed Jun. 25, 2001, now U.S. Pat. No. 6,563,554 B2issued May 13, 2003, which is a divisional of application Ser. No.09/217,931 filed on Dec. 22, 1998, now U.S. Pat. No. 6,281,952 issuedAug. 28, 2001, for which priority is claimed under 35 U.S.C. §120; andthis application claims priority of Application No. 9-359036 filed inJapan on Dec. 26, 1997 and Application No. 10-364247 filed in Japan onDec. 22, 1998, under 35 U.S.C. §119. The entire contents of all of theseapplications are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to liquid crystal displays used forinformation systems, such as word processors and notebook-type personalcomputers, video equipment of various kinds, video game machines,portable VCRs, digital cameras, etc. More particularly, the presentinvention relates to liquid crystal displays used indoors and outdoors,or in automobiles, air-planes, marine vessels, etc. where a variety ofambient light conditions occurs.

BACKGROUND OF THE INVENTION

Conventionally, CRTs (Cathode Ray Tubes), EL (Electroluminescence)elements, PDPs (Plasma Display Panels), etc. have been put intopractical use as displays of the light emissive type in which displaycontents can be overwritten electrically.

However, since this type of displays emit display light and use the samedirectly for the display, there arises a problem that their powerconsumption is quite large. Further since a light-emitting surface ofthe displays of this type serves as a display surface having highreflectance, if the displays of this type are used under thecircumstances where ambient light is brighter than the luminance, forexample, in direct sunlight, there always occurs a phenomenon known as“wash-out” in which the display light can not be observed.

On the other hand, liquid crystal displays have been put into practicaluse as color displays which display characters and/or images not byemitting the display light, but by adjusting an amount of transmittedlight from a particular light source. These liquid crystal displaysinclude a transmission type and a reflection type.

Of the two types, particularly popular are the liquid crystal displaysof the transmission type which employ a light source called “back light”at the back side, namely, behind the liquid crystal cell. Since theliquid crystal displays of the transmission type are advantageous inthinness and lightness, they have been used in diversified fields. Onthe other hand, the liquid crystal displays of the transmission typeconsume a large amount of power to keep the back light turned ON. Thus,regardless of the advantage that only a small amount of power isconsumed to adjust transmittance of the liquid crystal, a relativelylarge amount of power is consumed as a whole.

However, the liquid crystal displays of the transmission type (that is,color liquid crystal displays of the transmission type) wash out lessfrequently compared with the displays of the light emissive type. Thisis because, in the color liquid crystal displays of the transmissiontype, the reflectance on the display surface of a color filter layer isreduced by the reflectance reducing technique using a black matrix.

Nevertheless, it becomes too difficult to observe the display light onthe color liquid crystal displays of the transmission type when they areused under the circumstances where the ambient light is very strong andthe display light is relatively weak. This problem can be eliminated byusing brighter back light, but this solution raises another problem thatthe power consumption is further increased.

Unlike the displays of the light emissive type and liquid crystaldisplays of the transmission type, the liquid crystal displays of thereflection type show the display using the ambient light, therebyobtaining display light proportional to an amount of the ambient light.Thus, the liquid crystal displays of the reflection type areadvantageous in a principle that they do not wash out, and when used ina very bright place in direct sunlight, for example, the display can beobserved all the more sharply. Further, the liquid crystal displays ofthe reflection type do not use the back light for the display, andtherefore, have another advantage that the power for keeping the backlight turned ON can be saved. For the above reasons, the liquid crystaldisplays of the reflection type are particularly suitable as the devicesfor the outdoor use, such as portable information terminals, digitalcameras, and portable video cameras.

However, since these conventional liquid crystal displays of thereflection type use the ambient light for the display, the displayluminance largely depends on the surrounding environment, and when usedunder the circumstances where the ambient light is weak, there arises aproblem that the display content can not be observed. Particularly, incase that a color filter is used for realizing the color display, thecolor filter absorbs the light and the display becomes darker. Thus,when used under these circumstances, the above problem becomes moreapparent.

To eliminate the above problem, a lighting device called “front light”has been developed as an auxiliary light, so that the liquid crystaldisplays of the reflection type can be used under the circumstanceswhere the ambient light is weak. Since the liquid crystal displays ofthe reflection type have a reflection layer behind the liquid crystallayer, they can not use the back light as do the liquid crystal displaysof the transmission type. For this reason, the lighting device (frontlight) lights the liquid crystal displays of the reflection type fromthe front side, that is, from the display surface side.

On the other hand, liquid crystal displays, employing a transflectivefilm which transmits a part of incident light and reflects the rest,have been put into practical use as the liquid crystal displays whichcan be used under the circumstances where the ambient light is weakwhile maintaining the advantages of the liquid crystal displays of thereflection type. The liquid crystal displays using both the transmittedlight and reflected light are generally referred to as the liquidcrystal displays of the transflective type.

For example, Japanese Laid-open Patent Application No. 218483/1984(Tokukaisho No. 59-21843) (Japanese Patent Application No. 92885/1983(Tokugansho No. 58-92885)) discloses a liquid crystal display of thetransflective type which modulates the brightness by the TN (TwistedNematic) mode, STN (Super-Twisted Nematic) mode, etc., which are knownas the liquid crystal display modes for modulating the luminance of thetransmitted light. Also, Japanese Laid-open Patent Application No.318929/1995 (Tokukaihei No. 7-318929) discloses a liquid crystal displayof the transflective type, in which a transflective film is provided inclose proximity to the liquid crystal layer. Further, Japanese Laid-openPatent Application No. 160878/1994 (Tokukaihei No. 6-160878) (U.S. Pat.Nos. 5,598,285 and 5,737,051) discloses a liquid crystal display of thetransmission type adopting the in-plane switching method as a techniquefor realizing a wider range of viewing angles. However, since the liquidcrystal display of the transflective type disclosed in Japanese PatentApplication No. 218483/1984 (Tokukaisho No. 59-218483) has thetransflective film behind the liquid crystal cell seen from the viewer'sside, there occur the following problems (1) and (2).

(1) It is very difficult to set the brightness which affects avisibility of the display device. More specifically, when the brightnessof the liquid crystal display of the transflective type is setadequately for the reflection display, the brightness is set high, sothat it can be used under the circumstances where the ambient light isinsufficient. However, if the brightness is set high by using apolarization plate having high transmittance in the TN method, forexample, a contrast ratio, which is defined as a quotient obtained bydividing the brightness in the light display by the brightness in thedark display, becomes too low for the transmission display, therebydeteriorating the visibility. Conversely, when the brightness of theliquid crystal display of the transflective type is set adequately forthe transmission display, it is preferable to set the brightness in sucha manner as to raise the contrast ratio. However, in this case, thebrightness becomes too low for the reflection display, therebydeteriorating the visibility as well.

(2) In the reflection display, since the display is observed byreflecting the light having passed through the liquid crystal layersandwiched by the two substrates by the reflection film provided behindthe liquid crystal cell, there occurs parallax (double image) and theresolution deteriorates, thereby making high-resolution display verydifficult.

Also, in the liquid crystal display of the transflective type disclosedin Japanese Laid-open Patent Application No. 318929/1995 (Tokukaihei No.7-318929), since the transflective film is used as the reflection film,there arises another problem that there is no optical design such thatcan be suitable for both the reflection display section and transmissiondisplay section.

Further, although the in-plane switching method disclosed in JapaneseLaid-open Patent Application No. 160878/1994 (Tokukaihei No. 6-160878)is employed in the liquid crystal displays of the transmission type, thedirector configuration of the liquid crystal on the comb-shapedelectrode does not contribute to the display. This is not because, inmost cases, the electrode lines are made of metal that does not transmitlight, but because the director configuration of the liquid crystal isnot changed sufficiently for the transmission display.

SUMMARY OF THE INVENTION

Thus, to eliminate the above problems, the inventors of the presentinvention tried to apply the display method capable of eliminating theparallax and employed in the liquid crystal displays of the reflectiontype to the liquid crystal displays of the transflective type. Morespecifically, the inventors conducted an assiduous study by applying thetwo following methods to the transflective display:

(a) the GH (Guest-Host) method for filling liquid crystal compositionblended with a dichroic dye into the liquid crystal layer; and

(b) the reflection type liquid crystal display method using a singlepolarization plate (hereinafter, referred to as the single polarizationplate method).

To apply the above two display methods (a) and (b) which eliminate theparallax to the liquid crystal displays of the transflective type, thereflection layer is provided to touch or almost touch the liquid crystallayer, and a transmission opening is made through the reflection layerto use the transmitted light for the display in addition to thereflected light.

Then, the study revealed the following problems. In case of (a) GHmethod, when a concentration of the dichroic dye blended with the liquidcrystal composition is adjusted adequately for the reflection display,the brightness is sufficiently high but the contrast ratio becomes toolow in the transmission display section, thereby failing to obtainsatisfactory display. On the other hand, when a concentration of thedichroic dye blended with the liquid crystal composition is adjustedadequately for the transmission display, the contrast ratio issufficiently high in the transmission display section, but thebrightness becomes too low in the reflection display section, therebyfailing to obtain satisfactory display.

Also, in case of (b) single polarization plate method, the directorconfiguration of the liquid crystal and a thickness of the liquidcrystal layer which determine the optical characteristics, a voltageapplied to the liquid crystal for driving the same, etc. are setadequately for either the reflection display section or the transmissiondisplay realized by additionally providing a polarization plate or thelike behind the display surface (double polarization plate method).

Firstly, the display in the transmission display section when thethickness of the liquid crystal layer is set adequately for thereflection display will be explained. In this case, an amount of changein the polarization state caused when the director configuration of theliquid crystal layer is changed by an external field, such as anelectric field, is about a strength such that can realize a satisfactorycontrast ratio when incident light from the front, that is, from thedisplay surface side, passes through the liquid crystal layer and exitsto the display surface side by passing through the liquid crystal layeragain. However, when set in this manner, an amount of the change of thepolarization state of the light having passed through the liquid crystallayer is not sufficient in the transmission display section. Thus, evenif the polarization plate used for the transmission display alone isprovided behind the liquid crystal cell seen from the viewer's side inaddition to the polarization plate used for the reflection display andprovided to the viewer's side of the liquid crystal cell, that is, thedisplay surface side, the display in the transmission display section isnot satisfactory. In other words, when the director configurations(thickness of the liquid crystal layer, director configuration of theliquid crystal, etc.) of the liquid crystal layer are set to be suitablefor the reflection display, in the transmission display section, eitherthe brightness is not sufficient or even if the brightness issufficient, the transmittance does not decrease in the dark display,thereby failing to attain a sufficient contrast ratio for the display.

To be more specific, in case of the reflection display, the directorconfiguration of the liquid crystal in the liquid crystal layer iscontrolled by means of a voltage applied to the liquid crystal layer toimpart a phase difference of about ¼ wavelength to the light passingthrough the liquid crystal layer only once. When the transmissiondisplay is shown with the voltage modulation such that imparts a ¼wavelength phase modulation to the light passing through the liquidcrystal layer set in such a manner as to impart the above-specifiedphase difference to the light passing through the same, if thetransmittance of the transmission display section for the dark displayis lowered sufficiently, about half the luminance of the light isabsorbed by the polarization plate at the light outgoing side when thetransmission display section shows the light display, thereby failing toobtain satisfactory light display. If optical elements, such as apolarization plate and a phase difference compensation plate, areprovided to increase the brightness in the light display in thetransmission display section, the brightness in the dark display in thetransmission display section is increased to about half the brightnessin the light display, and the resulting contrast ratio is notsatisfactory for the display.

Next, the display in the reflection display section, in case that thedirector configurations of the liquid crystal layer are set to besuitable for the transmission display, will be explained. In case thatthe reflection display is shown when the liquid crystal layer is setadequately for the transmission display, the director configuration ofthe liquid crystal must be controlled by the voltage modulation in sucha manner that the polarization state of the light passing through theliquid crystal layer only once is modulated between the two polarizationstates which are orthogonal each other. The two orthogonal polarizationstates include two linearly polarized light beams having oscillationplanes intersecting at right angles, two circularly polarized lightbeams of right and left circularly polarization, or two ellipticallypolarized light beams having the same ellipticity whose major axisorientations intersect at right angles, thereby having opposite rotationdirections in their respective photo-electric fields. To realize themodulation of the polarization state in any combination of the above twopolarization states being orthogonal each other, a voltage must bemodulated in such a manner that the liquid crystal layer imparts a phasedifference of ½ wavelength to the light passing through the same. Whenthe polarization state of the light is modulated by any combination ofthe two orthogonal polarization states in the above manner, satisfactorybrightness and contrast ratio can be attained in the transmissiondisplay optionally, by the function of the polarization plate, with thehelp of the phase difference compensation plate.

However, when the liquid crystal layer is set to realize the abovecontrol, the reflectance in the reflection display is changed from thelight display to the dark display and to the light display again whilethe transmittance in the transmission display is changed once from thelight display to the dark display. Thus, the same display, that is,either the light or dark display, can not be realized simultaneously inthe reflection display section and transmission display section by thesame liquid crystal alignment changing means (for example, the thicknessof the liquid crystal layer is equal, the initial director configurationis identical, and the driving voltage is equal). The problems raised inthe methods (a) and (b) are also raised with the liquid crystal displayof the transflective type disclosed in aforementioned Japanese Laid-openPatent Application No. 318929/1995 (Tokukaihei No. 7-318929). Inaddition, a pressure detecting input device (touch panel) superimposedon the liquid crystal display has light reflecting properties, therebyposing a problem that the visibility is deteriorated. This problem isparticularly obvious in the liquid crystal displays of the reflectiontype.

Also, in general, a front light unit used to improve the visibility ofthe liquid crystal displays of the reflection type under thecircumstances where the ambient light is weak has a planar light pipestructure. Thus, the display content is observed through this lightpipe, and there arises a problem that the visibility is deteriorated.

The present invention is devised to solve the above problems, and it istherefore an object of the present invention to provide a liquid crystaldisplay with excellent visibility, capable of showing high-resolutiondisplay while using both the reflected light and transmitted light forthe display. It is another object of the present invention to provide aliquid crystal display with excellent visibility, capable of showinghigh-resolution color display while using both the reflected light andtransmitted light for the display.

The inventors of the present invention continued an assiduous study tofulfill the above and other objects, and achieved the present inventionwhen they discovered that the cause of the problems occurred in theconventional liquid crystal displays applying either the GH method orpolarization plate method is that the director configuration of theliquid crystal layer is set identical in the transmission displaysection and reflection display section at the same time.

Here, the director configuration of the liquid crystal layer indicatesnot only the director defined as orientation of the liquid crystalmolecules at a specific point in the liquid crystal layer, but also thevariation of the director field with respect to the position along thenormal axis of the liquid crystal layer.

To be more specific, to fulfill the above and other objects, a liquidcrystal display of the present invention is a liquid crystal displayfurnished with a liquid crystal display element having a pair ofsubstrates, to which alignment members are provided to their respectiveopposing surfaces, and a liquid crystal layer sandwiched by the pair ofsubstrates, characterized in that:

alignment mechanism for providing at least two different directorconfigurations simultaneously on different arbitrary regions used fordisplay in the liquid crystal layer is provided;

a reflecting member is provided to at least one of the differentarbitrary regions showing different director configurations; and

the different arbitrary regions showing different directorconfigurations are used for a reflection display section for showingreflection display and a transmission display section for showingtransmission display, respectively.

According to the above arrangement, the director configuration of theliquid crystal can be different simultaneously. Thus, for example, anamplitude of modulation in an opti-physical quantity, such as an amountof absorbed light (absorbance) in case that a light absorber like adichroic dye is used for the display, and a phase difference in casethat optical anisotropy is used for the display, can be changedseparately in each region having a different director configuration ofthe liquid crystal. Thus, according to the above arrangement, thetransmittance or reflectance based on an amplitude of modulation in anopti-physical quantity in response to the director configuration of theliquid crystal layer can be obtained, thereby making it possible to setthe optical parameters of the transmission display section and those ofthe reflection display section independently. Consequently, according tothe above arrangement, it has become possible to provide a liquidcrystal display of the transflective type with excellent visibility,capable of showing high-resolution display while using both thereflected light and transmitted light for the display.

Also, to fulfill the above and other objects, a liquid crystal displayof the present invention is a liquid crystal display furnished with aliquid crystal display element having a pair of substrates, to whichalignment members are provided to their respective opposing surfaces,and a liquid crystal layer sandwiched by the pair of substrates,characterized in that:

a region used for display in the liquid crystal layer is composed ofregions having at least two different thicknesses of the liquid crystallayer;

the regions having at least two different thicknesses are used for areflection display section and a transmission display section,respectively;

a reflecting member is provided at least to the reflection displaysection; and

the thickness of the liquid crystal layer is thinner in the reflectiondisplay section than in the transmission display section.

According to the above arrangement, the transmittance or reflectancebased on an amplitude of modulation in an opti-physical quantity in theregions having different thicknesses of the liquid crystal layer can beobtained, thereby making it possible to set the transmission displaysection and reflection display section independently. Thus, according tothe above arrangement, it has become possible to provide a liquidcrystal display of the transflective type with excellent visibility,capable of showing high-resolution display while using both thereflected light and transmitted light for the display.

According to the present invention, satisfactory display can be shown onboth the reflection display section and transmission display section byproviding the above arrangement to the liquid crystal display. However,there is an optimal ratio of the reflection display section to thetransmission display section for showing satisfactory display, and thisoptimal ratio varies depending on whether color display or monochromedisplay is desired, or whether the display is shown mainly by thereflection display or transmission display.

In the liquid crystal display of the present invention, in case thatboth the reflection display section and the transmission display sectionshow color display, it is preferable that an area of the reflectiondisplay section accounts for 30% or above and 90% and less of a total ofareas of the reflection display section and the transmission displaysection.

When the color display is shown on the liquid crystal display of thepresent invention in the above manner, besides the liquid crystal layer,design of the color filter layer, which plays an important role in colorreproduction, is critical. According to the study of the inventors ofthe present invention, the liquid crystal display of the transflectivetype will be used in typical two styles.

One is a style that mainly shows the transmission display in general useand uses the reflection display supplementarily, so that the wash-outcan be prevented under the lighting environment where the ambient lightis very strong, and therefore, can be used extensively in diversifiedlighting environments compared with the displays of the luminous type orthe liquid crystal displays of the transmission type. The other is astyle that mainly shows the reflection display in general use byexploiting the advantages of the reflection display that the powerconsumption is small and the lighting device known as the back light isturned ON only when used under the circumstances where the lighting isweak. Hence, like in the former style, this style can be usedextensively in diversified lighting environments.

In the former style (the style showing the transmission display mainly),by providing a color filter having a transmission color at least in thetransmission display section of the regions making up the region of eachpixel in at least one of the pair of substrates, it has become possibleto provide a liquid crystal display with excellent visibility, capableof showing high-resolution color display while using both the reflectedlight and transmitted light for the display.

When the color display is shown in the above manner, it is effective ifthe color filter having a transmission color is provided at least to thetransmission display section in each pixel, and in the reflectiondisplay section, either no color film is used or a color filter havingthe same brightness as the brightness of the color filter provided tothe transmission display section or a color filter having a transmissioncolor brighter than the brightness in the color filter provided to thetransmission display section, is provided at least partially.

In the latter style (the style showing the reflection display mainly),by providing a color filter having a transmission color at least in thereflection display section of the regions making up the display regionof each pixel in at least one of the pair of substrates, it has becomepossible to provide a liquid crystal display with excellent visibility,capable of showing high-resolution color display while using both thereflected light and transmitted light for the display.

When the color display is shown in the above manner, it is effective ifthe color filter having a transmission color is provided to at least thereflection display section in each pixel, and in the transmissiondisplay section, either no color film is used or a color filter havingchroma as good as the chroma of the color filter provided to thereflection display section or a color filter having a transmission colorwith better chroma than the chroma of the color filter provided to thereflection display section, is provided at least partially.

According to the above arrangement, it has become possible to provide aliquid crystal display with excellent visibility, capable of showing ahigh-resolution color display while using both the reflected light andtransmitted light for the display.

For a fuller understanding of the nature and advantages of theinvention, reference should be made to the ensuing detailed descriptiontaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section showing a major portion of a liquid crystaldisplay in accordance with Embodiment 1 of the present invention;

FIG. 2 is a view showing display characteristics of a liquid crystaldisplay of Example 1;

FIG. 3 is a view showing display characteristics of liquid crystaldisplays of Comparative Examples 2 and 3, respectively;

FIG. 4 is a cross section showing a major portion of a liquid crystaldisplay in accordance with Embodiment 2 of the present invention;

FIG. 5 is a view explaining a definition of a crossed rubbing angle;

FIG. 6 is a view showing display characteristics of a liquid crystaldisplay of Example 2;

FIG. 7 is a view showing display characteristics of a liquid crystaldisplay of Example 3;

FIG. 8 is a view showing display characteristics of a liquid crystaldisplay of Example 4;

FIG. 9 is a view showing display characteristics of a liquid crystaldisplay of Example 5;

FIG. 10 is a view showing display characteristics of a liquid crystaldisplay of Example 6;

FIG. 11 is a view showing display characteristics of a liquid crystaldisplay of Example 7;

FIG. 12 is a view showing display characteristics of a liquid crystaldisplay of Comparative Example 3;

FIG. 13 is a view showing display characteristics of a liquid crystaldisplay of Example 8;

FIG. 14 is a view showing display characteristics of a liquid crystaldisplay of Comparative Example 4;

FIG. 15 is a view showing display characteristics of a liquid crystaldisplay of Comparative Example 5;

FIG. 16 is a view showing display characteristics of a liquid crystaldisplay of Example 9;

FIG. 17 is a view showing the steps of the alignment treatment appliedto the substrates used for a liquid crystal display in accordance withEmbodiment 4 of the present invention;

FIGS. 18( a) through 18(e) are cross sections schematically showing thealignment treatment steps of FIG. 17;

FIG. 19 is a view showing display characteristics of a liquid crystaldisplay of Example 10;

FIG. 20 is a view showing display characteristics of a liquid crystaldisplay of Example 11;

FIG. 21( a) is a cross section showing a major portion of a liquidcrystal display of Example 12 when no voltage is applied;

FIG. 21( b) is a cross section showing the major portion of the liquidcrystal display of FIG. 21( a) when a voltage is applied;

FIG. 22 is a view showing display characteristics of a liquid crystaldisplay of Example 12;

FIG. 23( a) is a plan view showing a major portion of a TFT elementsubstrate for realizing a liquid crystal display of thetransmission-main transflective type in accordance with Embodiment 7 ofthe present invention;

FIG. 23( b) is a view showing a driving electrode of a reflectiondisplay section on the TFT element substrate of FIG. 23( a);

FIG. 23( c) is a view showing a transparent pixel electrode on the TFTelement substrate of FIG. 23( a);

FIG. 24 is a cross section of the TFT element substrate taken on lineA-A′ of FIG. 23( a);

FIG. 25 is a cross section of the TFT element substrate taken on lineB-B′ of FIG. 23( a);

FIG. 26( a) is a plan view showing a major portion of the liquid crystaldisplay of the transmission-main transflective type in accordance withEmbodiment 7 of the present invention, and it is a partial cutaway viewof a color filter substrate showing an alignment of color filters formedon the color filter substrate used in the above liquid crystal displayof the transmission-main transflective type with respect to atransmission display opening of a driving electrode formed in thereflection display section on the TFT element substrate of FIG. 23( a);

FIG. 26( b) is a cross section of the color filter substrate of FIG. 26(a);

FIG. 27 is a cross section showing a major portion of the liquid crystaldisplay taken on line C-C′ of FIG. 26( a);

FIG. 28 is a plan view showing a major portion of a TFT elementsubstrate for realizing a liquid crystal display of the reflection-maintransflective type in accordance with Embodiment 7 of the presentinvention;

FIG. 29( a) is a plan view showing a major portion of the liquid crystaldisplay of the reflection-main transflective type in accordance withEmbodiment 7 of the present invention, and it is a partial cutaway viewof a color filter substrate showing an alignment of color filters formedon the color filter substrate used in the above liquid crystal displayof the reflection-main transflective type with respect to a transmissiondisplay opening of a driving electrode formed in the reflection displaysection on the TFT element substrate of FIG. 28;

FIG. 29( b) is a cross section of the color filter substrate of FIG. 29(a);

FIG. 30 is a contour plot showing a relation of adapted luminance whichimparts perceived brightness of an equivalent value versus sampleluminance;

FIG. 31 is a view showing characteristics of a relation of illuminanceversus perceived brightness in a liquid crystal display of thetransflective type in accordance with Embodiment 8 of the presentinvention; and

FIG. 32 is a cross section schematically showing an arrangement of amajor portion of a liquid crystal display incorporating an input devicein accordance with Embodiment 11 of the present invention.

DESCRIPTION OF THE EMBODIMENTS

A liquid crystal display of the present invention is characterized inthat the director configuration of the liquid crystal can take differentstates respectively in the reflection display section and transmissiondisplay section at the same time. Here, the director configuration ofthe liquid crystal means not only the director defined as orientation ofthe liquid crystal molecules at a particular point in the liquid crystallayer, but also the variation of the director field with respect to theposition along the normal axis of the liquid crystal layer. Thus, in thepresent invention, methods of realizing different directorconfigurations of the liquid crystal in the reflection display sectionand transmission display section and alignment mechanisms used for thesemethods are classified into three categories, and each will be explainedseparately below.

In a first category method, the liquid crystal is given differentdirector configurations in the reflection display section andtransmission display section by means of an alignment mechanism formedto impose a specific condition of the liquid crystal layer differentlyin the reflection display section and transmission display section.

To be more specific, examples of the first category method include:

(1) using an alignment mechanism that twists the director of the liquidcrystal at totally different twist angles in the reflection displaysection and transmission display section;

(2) using an alignment mechanism that greatly changes the tilt angle ofthe director of the liquid crystal with respect to the substrates;

(3) providing liquid crystal materials of different kinds in thereflection display section and transmission display section; and

(4) blending different kinds of dyes with the liquid crystal material atdifferent concentrations in the transmission display section andreflection display section (in this case, a liquid crystal material ofthe same kind may be used in the transmission display section andreflection display section).

The liquid crystal display of the present invention is furnished withthe mechanism used for implementing the above methods as the alignmentmechanism of the present invention. The first category method and thealignment mechanism used for the first category method may be acombination of any of the above example methods (1) through (4), anddifferent director configurations of the liquid crystal can be realizedin the reflection display section and transmission display section bythe above example methods and the alignment mechanism used for theseexample methods.

In a second category method, the liquid crystal is given differentdirector configurations in the reflection display section andtransmission display section by display content overwriting means foroverwriting the display content with a time lapse (in other words, thealignment mechanism that makes the director configurations of the liquidcrystal different in the transmission display section and reflectiondisplay section is a display content overwriting means). The displaycontent overwriting means adopted in the second category method can beany of the existing display overwriting means.

More specifically, examples of the second category method include:

(5) overwriting the director configuration of the liquid crystal byusing different electrodes in the transmission display section andreflection display section as the alignment mechanism, in other words,applying different voltages as the display content overwriting meansdirectly to the reflection display section and transmission displaysection;

(6) applying substantially different voltages to the reflection displaysection and transmission display section from the same electrode. Inthis case, the liquid crystal is given with different directorconfigurations in the reflection display section and transmissiondisplay section driven by a common electrode by providing an insulationbody (for example, an insulation film) having different layerthicknesses in the reflection display section and transmission displaysection between the liquid crystal layer and the electrode driving thesame; and

(7) making the directions of the electric fields different in thereflection display section and transmission display section. In casethat the display is shown by changing the in-plane alignment directionof the liquid crystal of the liquid crystal layer by means of anelectrode group provided in parallel with one of the substratessandwiching the liquid crystal layer for supplying different potentialsto the liquid crystal layer, the director configurations of the liquidcrystal differ greatly at a region between the electrodes and a regionon the electrode. Thus, these regions having different directorconfigurations of the liquid crystal may be used for the reflectiondisplay and transmission display, respectively. Further, a method ofapplying different potentials to the liquid crystal layer alignedperpendicularly to the substrates by the same electrode group may beadopted. In case of adopting the second category method, the electrodesor insulation body used for implementing the above example methods, or acombination thereof corresponds to the alignment mechanism of thepresent invention, and naturally, the resulting liquid crystal displayis furnished with such alignment mechanism.

In a third category method, the director configurations of the liquidcrystal do not differ greatly, but the thicknesses of the liquid crystallayer, which are factors that determine the optical characteristics,differ in the reflection display section and transmission displaysection. To implement the third category method, an insulation filmhaving different thicknesses in the reflection display section andtransmission display section, substrates having different layerthicknesses or shapes in the reflection display section and transmissiondisplay section, etc. are used as the above alignment mechanism.

In case of adopting the third category method, the directorconfiguration of the liquid crystal may be twisted uniformly like in theTN method adopted in the liquid crystal display employing twopolarization plates, for example. In this case, the directorconfiguration of the liquid crystal is parallel to the substratessandwiching the liquid crystal layer, and the director is twisted whilechanging its direction in the plane of one of the substrates inaccordance with a distance from that substrate. When this directorconfiguration of the liquid crystal is adopted in the reflection displaysection and transmission display section by varying the thickness of theliquid crystal layer, satisfactory display can be realized both in thereflection display section and transmission display section, because theoptical characteristics vary with the thickness of the liquid crystallayer.

Also, in the GH method, since varying the thickness of the liquidcrystal layer can offer substantially the same effect as the effectobtained in case of changing the concentration of the dye, satisfactorydisplay can be realized both in the reflection display section andtransmission display section, even when the director configurations ofthe liquid crystal are substantially the same in the reflection displaysection and transmission display section.

As has been explained, the method for realizing different directorconfigurations of the liquid crystal in the reflection display sectionand transmission display section and the alignment mechanism used forthis method are classified into three categories, and the liquid crystaldisplay method used in the liquid crystal display of the presentinvention realized by the above method and alignment mechanism is notespecially limited, and can be selected from the methods using a changeof the director configuration of the liquid crystal for the display.Examples of the liquid crystal display method applicable in the presentinvention include: a mode using the nematic phase of the liquid crystalcomposition for the display, such as the TN method, STN method, nematicbistable mode, vertical alignment mode, hybrid alignment mode, and ECB(Electrically Controlled Birefringence) mode. Also, a mode usingscattering, such as the polymer dispersing type liquid crystal mode anddynamic scattering method, can be used as the above liquid crystaldisplay method. Further, the surface stabilized ferroelectric liquidcrystal display method using ferroelectric liquid crystal compositionand the thresholdless switching anti-ferroelectric liquid crystaldisplay method using anti-ferroelectric liquid crystal can be used asthe above liquid crystal display method of the present invention,because they also use a change of the director configuration of theliquid crystal for the display.

In case of adopting the third category method, the liquid crystaldisplay method used in the present invention can be a method of usingmodulation of the optical rotatory polarization like the TN method, amethod of using the modulation of the retardation like the ECB mode, ora method of modulating light absorption (absorbance) like the GH method.In case of adopting the third category method, besides the abovemethods, any method is applicable, provided that the thickness of theliquid crystal layer is a critical factor for determining the opticalcharacteristics, and provided that making the liquid crystal layer thickin the transmission display section and thin in the reflection displaysection can offer an effect of realizing satisfactory display.

As has been discussed, the liquid crystal display of the presentinvention is furnished with a liquid crystal display element having apair of substrates, to which alignment members (alignment means) areprovided to their respective opposing surfaces, and a liquid crystallayer sandwiched by the pair of substrates, and it is arranged in such amanner that: it is furnished with alignment mechanism for imparting atleast two different director configurations to arbitrary and differentareas in the liquid crystal layer used for the display simultaneously; areflecting member (reflecting means) is provided in at least one of theregions showing the different director configurations in the liquidcrystal layer; and the regions showing the different directorconfigurations are used as a reflection display section for showingreflection display and a transmission display section for showingtransmission display, respectively. This arrangement makes it possibleto obtain transmittance or reflectance based on an amplitude ofmodulation in an opti-physical quantity in response to the directorconfiguration of the liquid crystal layer, thereby realizing a highcontrast ratio without causing any parallax. Consequently, not only canthe visibility under dark circumstances be improved, but alsosatisfactory visibility can be obtained even when the ambient light isstrong.

To change an amplitude of modulation in an opti-physical quantity (suchas absorption of light and a phase difference caused by opticalanisotropy) in the reflection display section and transmission displaysection independently, even if the alignment direction of the liquidcrystal determined by the applied voltage is oriented to substantiallythe same direction across a region of the liquid crystal layer used forthe display, regions having different thicknesses of the liquid crystallayer can attain substantially the same effect as the effect obtainedwhen the alignment direction of the liquid crystal layer is changed inthese regions. For this reason, another liquid crystal display of thepresent invention is furnished with a liquid crystal display elementhaving a pair of substrates, to which alignment members (alignmentmeans) are provided to their respective opposing surfaces, and a liquidcrystal layer sandwiched by the pair of substrates, and it is arrangedin such a manner that:

a region used for display in the liquid crystal layer is composed ofregions having at least two different thicknesses of the liquid crystallayer;

the regions having at least two different thicknesses are used for areflection display section and a transmission display section,respectively;

a reflecting member (reflecting means) is provided at least to thereflection display section; and

the thickness of the liquid crystal layer is thinner in the reflectiondisplay section than in the transmission display section.

This arrangement also makes it possible to obtain transmittance orreflectance based on an amplitude of modulation in an opti-physicalquantity in regions having different thicknesses of the liquid crystallayer. Accordingly, the transmission display section and reflectiondisplay section can be set independently. Thus, according to the abovearrangement, a high contrast ratio can be attained without causing anyparallax, and not only can the visibility under dark circumstances beimproved, but also satisfactory visibility can be obtained even when theambient light is strong.

A liquid crystal display realizing satisfactory reflection display andtransmission display by changing the thickness of the liquid crystallayer in the reflection display section and transmission display sectionwill be explained mainly in Embodiments 1 and 2 below.

Embodiment 1

Mainly referring to FIG. 1, an example liquid crystal display adoptingthe GH method will be explained in the present embodiment.

FIG. 1 is a cross section of a major portion of the liquid crystaldisplay in accordance with the present embodiment. As shown in thedrawing, the liquid crystal display includes a liquid crystal cell 100(liquid crystal display element), and optionally, a back light 13(lighting device) serving as back light means. The liquid crystal cell100 and back light 13 are provided sequentially in this order from theviewer's (user's) side.

As shown in the drawing, the liquid crystal cell 100 is composed of aliquid crystal layer 1 sandwiched by an electrode substrate 101 (firstsubstrate) and an electrode substrate 102 (second substrate). Theelectrode substrate 101 has an alignment film 2 on a surface touchingthe liquid crystal layer 1 (an interface between the first substrate andthe liquid crystal layer 1), and the electrode substrate 102 has analignment film 3 on a surface touching the liquid crystal layer 1 (aninterface between the second substrate and the liquid crystal layer 1).

The electrode substrate 101 is composed of a substrate 4 made of, forexample, a light transmitting glass substrate on which are formed anelectrode 6 (voltage applying means) for applying a voltage to theliquid crystal layer 1, and the electrode 6 is covered with thealignment film 2 (alignment mechanism) to which the rubbing treatmenthas been applied.

On the other hand, the electrode substrate 102 provided in such a manneras to oppose the electrode substrate 101 through the liquid crystallayer 1 is composed of a light transmitting substrate 5 on which areformed counter electrodes 7 (voltage applying means) opposing theelectrode 6 through an insulation film 11 for applying a voltage to theliquid crystal layer 1.

The insulation film 11 is made in such a manner as to have differentfilm thicknesses in regions corresponding to a region of the liquidcrystal layer 1 used for the display, so that the above region of theliquid crystal layer 1 used for the display has at least two differentthicknesses of the liquid crystal layer (herein, exactly two differentthicknesses). To be more specific, the insulation film 11 is madethinner in the region corresponding to the transmission display section10 than in the region corresponding to the reflection display section 9.

In the region of the electrode substrate 102 corresponding to thereflection display section 9, a reflection film 8 (reflecting means) isformed to cover the electrodes 7, and further, the alignment film 3(alignment member, alignment mechanism) to which the rubbing treatmenthas been applied is formed to cover the electrodes 7 and reflection film8.

Here, each of the electrodes 6 and 7 is a transparent electrode made ofITO (Indium Tin Oxide), for example. Also, a voltage is applied to theelectrodes 6 and 7 to apply an electric field in the liquid crystallayer 1. Thus, the display is controlled by a voltage applied inaccordance with the display content.

Also, the reflection film 8 has light reflecting properties, and is madeof metal, such as aluminum or silver, or composed of dielectricmulti-layer film mirror. In case that the reflection film 8 is made of aconducting material, the reflection film 8 may also serve as anelectrode instead of the electrodes 7. In other words, the reflectionfilm 8 may be a reflective pixel electrode serving both as a liquidcrystal driving electrode for driving the liquid crystal layer 1 and thereflecting means. Further, the reflection film 8 may be a colorreflection film which reflects light having a wavelength in a rangeselected from the visible light, as the case may be.

It should be appreciated that the materials and producing methods ofeach member forming the electrode substrates 101 and 102 are not limitedto the above disclosure, and any known material and typical method areapplicable. Also, the arrangement of the liquid crystal display is notlimited to the above-described arrangement. For example, it may bearranged in such a manner that voltages are applied to the electrodes 6and 7 of the reflection display section 9 and transmission displaysection 10 directly from an exterior of the liquid crystal cell 100 inthe form of a signal from a touch panel (pressed coordinate detectingtype input means) or the like, which will be explained in embodimentsbelow. Also, active elements, such as TFT elements and MIM elements, maybe provided as the switching elements.

As shown in FIG. 1, the electrode substrates 101 and 102 are bonded toeach other with a sealing agent or the like in such a manner that theirrespective alignment films 2 and 3 oppose each other, and liquid crystalcomposition is filled into a space therebetween, whereby the liquidcrystal layer 1 is formed.

The back light 13 is provided behind the liquid crystal cell 100 seenfrom the viewer's (user's) side, that is, at the back side of theelectrode substrate 102. The back light 13 is mainly composed of a lightsource 13 a and a light pipe 13 b. For example, the light source 13 a isprovided along the side surface of the light pipe 13 b, and accordingly,the light pipe 13 b receives light emitted from the light source 13 a onthe side surface where it is provided, and emits the received light toan object, namely, the liquid crystal cell 100. Here, any existinglighting device can be used as the back light 13.

In the above-arranged liquid crystal display, the reflection displaysection 9 on which is formed the reflection film 8 shows the display bycontrolling the reflection luminance of the ambient light incident onthe display surface from the substrate 4 side, that is from the viewer'sside, by changing the director configuration of the liquid crystal. Thetransmission display section 10 on which is formed no reflection film 8shows the display by controlling the luminance of the transmitted lightincident on the display surface from the substrate 5 side by changingthe director configuration of the liquid crystal. In this case, lightemitted from the back light 13 provided behind the liquid crystal cell100 may be used, as the case may be.

As has been explained, the liquid crystal display of FIG. 1 is assembledin such a manner as to have different thicknesses of the liquid crystallayer in the reflection display section 9 and transmission displaysection 10. Consequently, the present liquid crystal display hassubstantially different director configurations of the liquid crystal inthe reflection display section 9 and transmission display section 10.

Here, the arrangement of the liquid crystal display having differentthicknesses in the reflection display section 9 and transmission displaysection 10 will be explained in the following.

The liquid crystal layer can be given different thicknesses in thereflection display section 9 and transmission display section 10, forexample, by providing the insulation film 11 having differentthicknesses in the reflection display section 9 and transmission displaysection 10 as shown in FIG. 1.

In order to vary the thickness of the liquid crystal layer in thereflection display section 9 and transmission display section 10, it issufficient if at least one of the substrates (electrode substrates 101and 102) sandwiching the liquid crystal is arranged in the above manner.

Therefore, the insulation film 11 is not necessarily provided on thesubstrate 4 and it can be provided on the substrate 5 instead. Even inthis case, the reflection film 8 is provided on the substrate 5 on theelectrode substrate 102 side (that is, opposing side to the displaysurface side (electrode substrate 101 side) through the liquid crystallayer 1).

In the liquid crystal display of FIG. 1, the thickness of the liquidcrystal layer is changed in the reflection display section 9 andtransmission display section 10 by changing the thickness of theinsulation film 11 in a region corresponding to the reflection displaysection 9 and a region corresponding to the transmission display section10. However, the same can be realized by forming the substrate 4 or 5 itself in exactly the same shape as the insulation film 11 of FIG. 1.

When the thickness of the insulation film 11 is changed in the regioncorresponding to the reflection display section 9 and the regioncorresponding to the transmission display section 10, the insulationfilm 11 on the region corresponding to the transmission display section10 is made thinner than the insulation film 11 on the regioncorresponding to the reflection display section 9 as shown in FIG. 1, orthe insulation film 11 is formed on the region corresponding to thereflection display section 9 alone, and not on the region correspondingto the transmission display section 10.

Further, the thickness of the liquid crystal layer in the reflectiondisplay section 9 or in the transmission display section 10 is keptconstant by providing spacers (not shown) to the liquid crystal layer 1or by any other applicable means. For example, when spherical spacersare provided to the liquid crystal layer 1, the thickness of the thinnerliquid crystal layer in the reflection display section 9 is almost aslarge as the diameter of the spacers.

The liquid crystal layer 1 sandwiched by a pair of the substratesprepared in the above manner, that is, the electrode substrates 101 and102, is made of the liquid crystal composition as previously mentioned.As the liquid crystal display method using the liquid crystal layer 1,the GH method may be used, in which the liquid crystal compositionprepared by blending a dichroic dye 12 with liquid crystal is used asshown in FIG. 1, and the director configuration of the liquid crystaland the alignment direction of the dichroic dye 12 are changedsimultaneously upon application of an electric field in the liquidcrystal layer 1, so that the display is shown using the variance of theabsorption coefficient caused by the dichroism.

Next, the following will explain, with reference to FIG. 1, the actionof the liquid crystal layer 1 in the GH method, and the displayprinciple in case that the thicknesses of the liquid crystal layer aredifferent in the reflection display section 9 and transmission displaysection 10.

When the display is shown on the liquid crystal display of FIG. 1, thedisplay is shown in the transmission display section 10 by letting lightemanated from the back light 13 or the like behind the liquid crystallayer 1 pass through the liquid crystal layer 1 only once and go outfrom the display surface as the display light as is indicated by anarrow. Here, the dichroic dye 12 blended in the liquid crystalcomposition in the liquid crystal layer 1 changes its light absorbancein response to the director configuration of the liquid crystal. Thus,when the liquid crystal is aligned in parallel with the display surface(electrode substrate 101) as shown in a transmission display section 10a (which is referred to as planer alignment, hereinafter), the dichroicdye 12 in this region absorbs most of the light passing through theliquid crystal layer 1, and the transmission display section 10 showsthe dark display. On the other hand, when the liquid crystal is alignedperpendicular to the display surface (electrode substrate 101) as shownin a transmission display section 10 b, (which is referred to as thevertical alignment), the dichroic dye 12 absorbs a smaller amount of thelight, and the transmission display section 10 shows the light display.

By contrast, the reflection display section 9 uses the light incident onthe display surface from the viewer's side for the display. To be morespecific, as is indicated by an arrow, the light incident on the displaysurface passes through the liquid crystal layer 1 is reflected by thereflection film 8, passes through the liquid crystal layer 1 again, andexits from the display surface as the display light. Here, when theliquid crystal is aligned in parallel with the display surface as shownin a reflection display section 9 a, the dichroic dye 12 in this regionabsorbs most of the light, and the reflection display section 9 showsthe dark display. On the other hand, when the liquid crystal is alignedperpendicular to the display surface as shown in a reflection displaysection 9 b, the dichroic dye 12 in this region absorbs less amount ofthe light, and the reflection display section 9 shows the light display.

Thus, the light display and dark display can be shown by controlling thedirector configuration of the liquid crystal by supplying a potentialdifference between the electrodes 6 and 7. In this case, the initialdirector configuration of the liquid crystal is not especially limited.For example, the liquid crystal may be aligned in parallel with thedisplay surface or twisted further when no voltage is applied.Conversely, the liquid crystal may be aligned perpendicular to thedisplay surface when no voltage is applied. In the former case (parallelwhen no voltage is applied or further with a twist), liquid crystalhaving positive dielectric constant anisotropy can be used. On the otherhand, in the latter case, (perpendicular when no voltage is applied),liquid crystal having negative dielectric constant anisotropy can beused. As has been explained, the initial director configuration of theliquid crystal is not especially limited, but it is necessary to adjustthe thickness of the insulation film 11 in such a manner as to secure athickness of the liquid crystal layer suitable for the directorconfiguration of the liquid crystal to be used.

Here, for ease of production of the liquid crystal layer 1, liquidcrystal layer 1, as in typical liquid crystal displays, is preferablyprovided continuously across the reflection display section 9 andtransmission display section 10 or a plurality of display pixels, asshown in FIG. 1.

Even when the liquid crystal layer 1 is provided across the reflectiondisplay section 9 and transmission display section 10, if thethicknesses of the liquid crystal layer are different in the reflectiondisplay section 9 and transmission display section 10, a distance thelight travels by passing through the liquid crystal layer 1 only once inthe transmission display section 10 to serve as the display light in theend can be set equal to a distance the light travels by passing andreturning through the liquid crystal layer 1 in the reflection displaysection 9.

Thus, the reflection brightness in the reflection display section 9 andthe transmission brightness in the transmission display section 10 canbe set to substantially the same level, and the contrast ratios in thereflection display section 9 and transmission display section 10 can bealso set to substantially the same value. In other words, in the GHmethod using the light absorption by the dichroic dye 12, providingdifferent thicknesses of the liquid crystal layer in the reflectiondisplay section 9 and transmission display section 10 can offersubstantially the same effect as the effect offered by changing theconcentration of the dye, and therefore, by so doing, the adequateconcentration of the blended dichroic dye 12 in the reflection displaysection 9 and the adequate concentration of the blended dichroic dye 12in the transmission display section 10 can be set to substantially thesame value. Consequently, the reflection display section 9 andtransmission display section 10 can show satisfactory displaysimultaneously both in the reflection display section 9 and transmissiondisplay section 10 by means of the liquid crystal layer 1 providedacross the reflection display section 9 and transmission display section10. In short, both the display contrast ratio and brightness in thelight display become substantially equal in the reflection displaysection 9 and transmission display section 10.

Herein, “brightness” is defined as a ratio of the incident light on theliquid crystal layer 1 observed by the viewer as the display light ineither the reflection display section 9 or transmission display section10, and “contrast ratio” is defined as the quotient obtained by dividingthe brightness in the light display by the brightness in the darkdisplay.

Generally, the contrast ratio suitable for the transmission display mustbe higher than the contrast ratio suitable for the refection display.Thus, in order to realize satisfactory display, compared with a case ofsetting the equal contrast ratio in the reflection display section 9 andtransmission display section 10 to satisfy the above requirement, it ismore effective to set the contrast ratio higher in the transmissiondisplay section 10 than in the reflection display section 9 by settingthe thickness of the liquid crystal layer larger in the transmissiondisplay section 10 than in the reflection display section 9.

In the following, the liquid crystal display of the present embodimentwill be explained based on the above-described display principle andwith reference to FIGS. 1 through 3 by way of an example and comparativeexamples for purposes of explanation only, without any intention as adefinition of the limits of the invention.

Example 1

Explained in the present example is a liquid crystal display employingthe liquid crystal layer 1 adopting the GH method, in which the liquidcrystal having the negative dielectric constant anisotropy alignssubstantially perpendicular to the display surface when no voltage isapplied to the liquid crystal layer 1 and tilts with respect to thedisplay normal when a voltage is applied to the liquid crystal layer 1.First, the following will explain a method of manufacturing the liquidcrystal display.

Initially, a 140 nm-thick ITO film is sputtered over the transparentsubstrate 4, which is etched by photolithography, whereby the electrode6 (transparent electrode) of a predetermined pattern is formed. Here, aglass substrate is used as the substrate 4.

Next, a vertical aligning alignment film is provided to the substrate 4by the offset printing on the surface where the electrode 6 is formed,and the substrate 4 is baked at 200 C in an oven, whereby the alignmentfilm 2 is formed. Subsequently, the alignment treatment is applied tothe alignment film 2 by means of rubbing, and as a consequence, theelectrode substrate 101 which serves as the substrate on the viewer'sside is produced.

The vertical aligning alignment film originally has the properties suchthat align the liquid crystal along the normal direction of the filmsurface, and the alignment treatment like the rubbing changes theproperties to the properties such that tilt the director configurationof the liquid crystal by several degrees with respect to the normaldirection. After a voltage is applied to the liquid crystal layer 1, thetilt thus conferred tilts the director configuration of the liquidcrystal much further toward the above alignment treatment direction.

In the meantime, insulation photosensitive resin is applied over thesubstrate 5 by spin coating, and UV rays are irradiated to thephotosensitive resin masked in such a manner that no photosensitiveresin is left in the transmission display section 10, while a 3 m-thicklayer of the photosensitive resin is formed in the reflection displaysection 9, whereby a predetermined pattern of the insulation film 11 isformed. The pattern edge portion of the insulation film 11 is made insuch a manner as to form gentle steps, so that the electrode 7 whichwill be formed later will not be broken by a difference in steps of theinsulation film 11. As with the substrate 4, a transparent glasssubstrate is used as the substrate 5.

Further, a 140 nm-thick ITO film is sputtered over the substrate 5 onthe surface where the insulation film 11 is formed, over which a 200nm-thick aluminum film, which will serve as a light reflectiveelectrode, is sputtered. Then, the aluminum film thus formed ispatterned by photolithography and dry etching in such a manner as toleave the aluminum film in the reflection display section 9 alone (wherethe photosensitive resin was left when the photosensitive resin waspatterned to form the insulation film 11), whereby the reflection film 8is formed. Further, the ITO film beneath the reflection film 8 is etchedby photolithography to form the electrodes 7 (transparent electrode) ofa predetermined pattern.

Subsequently, the alignment film 3 is formed over the substrate 5 on thesurface where the electrodes 7 and reflection film 8 are formed in thesame manner as the alignment film 2 formed on the electrode substrate101 serving as the substrate on the viewer's side. Then, the alignmenttreatment is applied to the alignment film 3 by means of rubbing,whereby the electrode substrate 102 is produced.

Then, as a sealing agent, sealing resin (not shown) is provided aroundone of the electrode substrates 101 and 102 produced in the abovemanner, and plastic spherical spacers having a diameter of 4.5 m arescattered over the other electrode substrate on the surface where thealignment film is formed. Then, as shown in FIG. 1, the electrodesubstrates 101 and 102 are placed to oppose each other with theirelectrode surfaces inside, and the sealing resin is cured under appliedpressure, whereby a liquid crystal cell for filling is produced. Fillingspaces (thicknesses of the liquid crystal layer 1) into which the liquidcrystal will be filled in the refection display section 9 andtransmission display section 10 of the liquid crystal cell for fillingwere measured by means of the reflected light spectrum, and were 4.5 macross and 7.5 m across, respectively.

Further, a concentration of the dichroic dye 12, blended with the liquidcrystal having the negative dielectric constant anisotropy to producethe liquid crystal composition filled in the liquid crystal cell forfilling is adjusted in such a manner that a satisfactory contrast ratiocan be attained both in the reflection display section 9 andtransmission display section 10. Further, a chiral dopant for impartingtwist to the director configuration of the liquid crystal is added tothe liquid crystal composition, so that, with the alignment treatmentapplied to the alignment films 2 and 3, the chiral dopant imparts thesame twist to the director configuration of the liquid crystal in theliquid crystal layer 1 sandwiched by the electrode substrates 101 and102 above and beneath in the reflection display section 9 andtransmission display section 10 when a voltage is applied for the darkdisplay. Then, the liquid crystal cell for filling is filled with theliquid crystal by means of vacuum injection, whereby the liquid crystaldisplay is assembled.

A voltage was applied to the liquid crystal layer 1 while measuring thereflectance of the reflection display section 9 and transmittance of thetransmission display section 10 of the liquid crystal display thusobtained through a microscope, and the display characteristics graphedin FIG. 2 were obtained. The voltage applied to the liquid crystal layer1 is a rectangular pulse inverting every 17 msec. In the drawing, thehorizontal axis represents a root mean square value of the appliedvoltage, and the vertical axis represents the brightness (reflectance ortransmittance). Also, in the drawing, a curve 111 represents the voltagedependence of the reflectance in the reflection display section 9 and acurve 112 represents the voltage dependence of the transmittance in thetransmission display section 10.

As the curves 111 and 112 reveal, the brightness (reflectance ortransmittance) in the reflection display section 9 and transmissiondisplay section 10 of the above liquid crystal display decreases with anincreasing applied voltage. That is, when the applied voltage is 1.8V,the reflectance of the reflection display section 9 and transmittance ofthe transmission display section 10 are 55% and 52%, respectively, andwhen the applied voltage is increased to 5V, both decrease to 11% and10%, respectively.

In other words, in the above liquid crystal display, both the reflectiondisplay section 9 and transmission display section 10 can realize thedisplay with excellent visibility, attaining high brightness exceeding50% in the light display and a contrast ratio of about 5.

Comparative Example 1

A comparative example with respect to Example 1 will be explained in thefollowing. In the present comparative example, a comparative liquidcrystal display adopting the GH method was assembled in the same manneras Example 1 except that the thicknesses of the liquid crystal layerwere equal in the reflection display section 9 and transmission displaysection 10.

More specifically, in the present comparative example, the insulationfilm 11 formed over the substrate 5 in Example 1 was omitted, so thatthe liquid crystal display was assembled in such a manner that thethickness of the liquid crystal layer was 4.5 m in both the reflectiondisplay section 9 and transmission display section 10. In other words, acomparative liquid crystal cell for filling was produced, in which thereflection display section 9 and transmission display section 10 areflat on both the electrode substrates opposing and sandwiching theliquid crystal layer 1 above and beneath, and the liquid crystalcomposition blended with the dichroic dye 12 and chiral dopant used inExample 1 were also filled into the comparative liquid crystal cell forfilling, whereby the comparative liquid crystal display was assembled.

The reflectance of the reflection display section 9 and transmittance ofthe transmission display section 10 of the above comparative liquidcrystal display were measured in the same manner as Example 1, and theresulting display characteristics are graphed in FIG. 3.

Comparative Example 2

In the present comparative example, a comparative liquid crystal displaywas assembled in such a manner that liquid crystal composition havinghigher concentration of the dichroic dye 12 than the one in ComparativeExample 1 was filled into a comparative liquid crystal cell for fillingof the same type as the one used in Comparative Example 1, so that thebrightness and contrast ratio become optimal for the transmissiondisplay section 10.

The reflectance of the reflection display section 9 and transmittance ofthe transmission display section 10 of the above comparative liquidcrystal display were measured in the same manner as Example 1, and theresulting display characteristics are also graphed in FIG. 3.

In FIG. 3, the horizontal axis represents a root mean square value ofthe applied voltage, and the vertical axis represents the brightness(reflectance or transmittance). Also, in the drawing, a curve 121represents the voltage dependence of the reflectance in the reflectiondisplay section 9 and a curve 122 represents the voltage dependence ofthe transmittance in the transmission display section 10 in ComparativeExample 1, whereas a curve 123 represents the voltage dependence of thereflectance in the reflection display section 9 and a curve 124represents the voltage dependence of the transmittance in thetransmission display section 10 in Comparative Example 2.

As the curves 121 and 122 reveal, the brightness (reflectance andtransmission) in the reflection display section 9 and transmissiondisplay section 10 of the comparative liquid crystal display ofComparative Example 1 decreases with an increasing applied voltage. Thatis, when the applied voltage is 1.8V, the reflectance in the reflectiondisplay section 9 and transmittance in the transmission display section10 are 55% and 66%, respectively. When the applied voltage is increasedto 5V, both decrease to 11% and 22%, respectively.

In other words, in the comparative liquid crystal display of ComparativeExample 1, high brightness exceeding 50% and a satisfactory contrastratio of about 5 were attained in the reflection display section 9,whereas in the transmission display section 10, high brightness wasattained but a contrast ratio was as low as 3, thereby deteriorating thedisplay quality. This happens because the thickness of the liquidcrystal layer 1 is equal in the reflection display section 9 andtransmission display section 10.

Also, as the curves 123 and 124 reveal, the brightness (reflectance andtransmission) of the reflection display section 9 and transmissiondisplay section 10 of the comparative liquid crystal display ofComparative Example 2 decreases with an increasing applied voltage. Thatis, when the applied voltage is 1.8V, the reflectance of the reflectiondisplay section 9 and the transmittance of the transmission displaysection 10 are 29% and 51%, respectively. When the applied voltage isincreased to 5V, both decrease to 3% and 10%, respectively.

In other words, in the comparative liquid crystal display of ComparativeExample 2, high brightness exceeding 50% and a satisfactory contrastratio of about 5 were attained in the transmission display section 10,whereas in the reflection display section 9, a contrast ratio as high as10 was attained but the brightness was below 30%, and the display shownthereon was dark. This happens because the thickness of the liquidcrystal layer 1 is equal in the reflection display section 9 andtransmission display section 10.

The above comparison of Example 1 with Comparative Examples 1 and 2reveals that, with the liquid crystal display adopting the GH method, itis effective to set the thickness of the liquid crystal layer 1 largerin the transmission display section 10 than in the reflection displaysection 9 to make the contrast ratio of the transmission display section10 as high as or higher than the contrast ratio of the reflectiondisplay section 9.

Embodiment 2

The liquid crystal display of Embodiment 1 adopts the GH method, butliquid crystal displaying methods other than the GH method are alsoapplicable. For example, another applicable method is shown in FIG. 4,in which the substrates 4 and 5 are sandwiched by polarization plates 14and 15, so that the retardation or optical rotatory polarization (whichare collectively referred to as polarization converting function) of theliquid crystal layer 1 is used for the display.

In the present embodiment, a liquid crystal display using thepolarization converting function will be explained with reference toFIG. 4 mainly. Hereinafter, like components are labeled with likereference numerals with respect to Embodiment 1, and, for ease ofexplanation, the description of these components is not repeated here.

FIG. 4 is a cross section showing a major portion of the liquid crystaldisplay of the present embodiment. The liquid crystal display of FIG. 4includes a liquid crystal cell 200 (liquid crystal element), andoptionally, the back light 13 (lighting device), which are sequentiallyprovided in this order from the viewer's (user's) side.

As shown in FIG. 4, the liquid crystal cell 200 includes the liquidcrystal layer 1 sandwiched by an electrode substrate 201 (firstsubstrate) and another electrode substrate 202 (second substrate). Theelectrode substrate 201 has the alignment film 2 on a surface touchingthe liquid crystal layer 1 (an interface between the first substrate andthe liquid crystal layer 1), and the electrode substrate 202 has thealignment film 3 on a surface touching the liquid crystal layer 1 (aninterface between the second substrate and the liquid crystal layer 1).Further, the liquid crystal cell 200 includes a phase differencecompensation plate 16 and the polarization plate 14 at the outside ofthe electrode substrate 201 (the opposite side from the side facing theelectrode substrate 202), and a phase difference compensation plate 17and the polarization plate 15 at the outside of the electrode substrate202 (the other side across the side opposing the electrode substrate201). The phase difference compensation plates 16 and 17 are used onlywhen necessary.

Phase difference compensation plates of various kinds, such as astretched polymer film, a polymer film of fixed orientation of itsliquid crystalline phase, and a liquid crystal polymer film, can be usedas the phase difference compensation plates 16 and 17 used optionally inthe present embodiment. The optical functions of the phase differencecompensation plates 16 and 17 are used to (1) prevent the coloring oftencaused when the phase difference compensation plates 16 and 17 areomitted, (2) change the dependence of the brightness on the potentialdifference between the electrodes 6 and 7, (3) change the viewing anglecharacteristics, etc.

Also, the electrode substrate 201 is composed of the substrate 4 madeof, for example, a light-transmitting glass substrate on which is formedthe electrode 6 for applying a voltage to the liquid crystal layer 1,and the electrode 6 is covered with the alignment film 2 to which therubbing treatment has been applied.

On the other hand, the other electrode substrate 202 provided to opposethe electrode substrate 201 through the liquid crystal layer 1 iscomposed of the light-transmitting substrate 5 on which are formed theelectrodes 7 for applying a voltage to the liquid crystal layer 1 ascounter electrodes opposing the electrode 6 through the insulation film11. Note that, however, the liquid crystal display of FIG. 4 is arrangedin such a manner that the electrodes 7 in the reflection display section9 and the electrodes 7 in the transmission display section 10 areelectrically isolated, so that a voltage is applied to each separatelyfrom outside the liquid crystal cell. The reflection film 8 is formed onthe electrode substrate 202 at a region corresponding to the reflectiondisplay section 9, and the liquid crystal alignment film 3 to which therubbing treatment has been applied is formed to cover the electrodes 7and reflection film 8. The insulation film 11 is formed thinner in aregion corresponding to the transmission display section 10 than in aregion corresponding to the reflection display section 9.

As shown in FIG. 4, the electrode substrates 201 and 202 are bonded toeach other by a sealing agent or the like while opposing each other withtheir respective alignment films 2 and 3 inside, and the liquid crystalcomposition is filled in a space therebetween, whereby the liquidcrystal layer 1 is formed.

In the light display shown on the above liquid crystal display, theliquid crystal layer 1 made of the above-described liquid crystalcomposition is provided continuously across the reflection displaysection 9 and transmission display section 10. In FIG. 4, the liquidcrystal in the liquid crystal layer 1 effects the polarizationconverting function to the light passing through the liquid crystallayer 1 when aligned in parallel with the display surface as shown inthe reflection display section 9 b and transmission display section 10b, and as a consequence, for example, the dark display is shown. On theother hand, the liquid crystal in the liquid crystal layer 1 hardlyeffects the polarization converting function when alignedperpendicularly to the display surface as shown in the reflectiondisplay section 9 a and transmission display section 10 a, and as aconsequence, for example, the light display is shown.

Thus, the light display and dark display can be shown by using thechange in the alignment in the reflection display sections 9 a and 9 band the transmission display sections 10 a and 10 b as the change inluminance of the display light by the linearly polarized light selectivetransmission function effected by the polarization plate 14 on thedisplay surface side and the polarization plate 15 on the back light 13side sandwiching the liquid crystal layer 1. In this case, as previouslymentioned, the phase difference compensation plates 16 and 17 as shownin FIG. 4 may be used to compensate the wavelength dependence of adifference of the refractive index of the liquid crystal layer 1, tochange the voltage dependence of the brightness modulated by the liquidcrystal layer 1, or to change the viewing angle characteristics, as thecase may be.

When using the optical anisotropy for the display in the above manner,the initial director configuration of the liquid crystal is notespecially limited, and for example, the liquid crystal layer 1 can bealigned either in parallel with or perpendicular to the display surfacewhen no voltage is applied. In the former case (aligned parallel when novoltage is applied), liquid crystal having the positive dielectricconstant anisotropy is used, while in the latter case (alignedperpendicular when no voltage is applied), liquid crystal having thenegative dielectric constant anisotropy is used.

As has been explained, the initial director configuration of the liquidcrystal is not especially limited when the optical anisotropy is usedfor the display, but it is effective to adjust a thickness of theinsulation film 11 in such a manner as to secure a suitable thickness ofthe liquid crystal layer for the director configuration of the liquidcrystal to be used.

In order to realize the dark display in the reflection display section9, light is first converted to linearly polarized light by thepolarization plate 14. Then, the polarization state is changed by thephase difference compensation plate 16 when necessary, and thepolarization state is further changed by the liquid crystal layer 1 inthe reflection display section 9 which is thinner than the transmissiondisplay section 10. Here, the necessary condition for the idea darkdisplay is to covert the polarization state on the reflection film 8 tocircularly polarized light whether right or left in the end. Also, thenecessary condition to realize the idea light display in the reflectiondisplay section 9 is to convert the polarization state on the reflectionfilm 8 to the linearly polarized light. If the director configuration ofthe liquid crystal can be controlled electrically between the darkdisplay and light display, the display states can be switched.

In other words, there must be substantially a difference of ¼ wavelength(approximately 90) between the phase difference (phase difference of thedisplay light on the reflection film 8) imparted to the travelling lightby the liquid crystal layer 1 before it reaches the reflection film 8when realizing the dark display, and a phase difference (phasedifference of the display light on the reflection film 8) imparted tothe travelling light by the liquid crystal layer 1 before it reaches thereflection film 8 when realizing the light display, and the directorconfiguration of the liquid crystal realizing the above condition has tobe controlled electrically, that is, the director configuration of theliquid crystal has to be controlled between the ones, one gives thecircularly polarized light in the dark display, and the other gives thelinearly polarized light in the light display, on the reflection film 8.Here, the linearly polarized light on the reflection film 8 to realizethe light display can take any direction of polarization.

In the transmission display section 10, incident light is converted tothe linearly polarized light by the polarization plate 15, and itspolarization state is changed by the phase difference compensation plate17 when necessary, and the polarization state is converted further bythe liquid crystal layer 1 formed thicker than in the reflection displaysection 9. Finally, the polarization state is changed by the phasedifference compensation plate 16 when necessary, and the light exitsthrough the polarization plate 14, whereby the display is shown.

In the reflection display section 9, it is the change of thepolarization state of the light immediately before it enters thepolarization plate 14 that is used for the display. Thus, to show thelight display, the polarization state of the light immediately before itenters the polarization plate 14 is adjusted to be linearly polarizedlight having an oscillating direction along the transmission axisorientation of the polarization plate 14. On the other hand, to show thedark display, the polarization state of the light immediately before itenters the polarization plate 14 is adjusted to be linearly polarizedlight having an oscillation plane along the absorption axis orientationof the polarization plate 14.

In other words, the display can be switched if a change of the directorconfiguration of the liquid crystal 1 can be controlled electricallywith the voltage application over a range such that can make adifference of substantially ½ wavelength (approximately 180) between thephase difference (phase difference of the display light going outthrough the liquid crystal layer 1) imparted to the light passingthrough the liquid crystal layer 1 in the transmission display section10 for the light display, and the phase difference (phase difference ofthe display light going out through the liquid crystal layer 1) impartedto the light passing through the liquid crystal layer 1 in thetransmission display section 10 for the dark display.

The phase control of ½ wavelength means to control the polarizingorientation of the linearly polarized light immediately before it entersthe polarization plate 14 from liquid crystal layer 1, and polarizationconversion function which includes not only the control of the phasedifference caused by the retardation whose major axis of the refractiveindex is aligned uniformly parallel, but also the polarization rotationphenomenon, in which the major axis of the refractive index of theliquid crystal layer 1 is twisted along the twist of the directorconfiguration of the liquid crystal, and the polarizing orientation ofthe linearly polarized light changes in response to the twist of thedirector, which varies with the voltage. Actual polarization convertingfunction to realize the above control is the one controlling over twoorthogonal polarization states of general kind, when the application ofthe phase difference compensation plates 16 and 17 is concerned.

Examples of director configurations of the liquid crystal which realizethe polarization converting function realizing the control of thepolarization state (phase control of light) described above are:director configuration uniformly parallel to the substrates 4 and 5(parallel to the display surface) (homogenous alignment); directorconfiguration parallel to the substrates 4 and 5 (parallel to thedisplay surface) and twisted between the substrates 4 and 5 (an intervalbetween the substrates sandwiching the liquid crystal layer 1 above andbeneath) (twist alignment); and director configuration perpendicular tothe substrates 4 and 5 (perpendicular to the display surface)(homeotropic alignment). Further, the hybrid director configurationhaving planer alignment on one of the interfaces of the liquid crystallayer 1 and vertical alignment on the other interface and the like canbe used as well.

In case of the twist alignment, it is preferable that the liquid crystalis twisted by an angle in a range between 60 and 100 inclusive, or 0 and40 inclusive between the substrates 4 and 5.

This is because the conditions suitable for both the reflection displaysection 9 and transmission display section 10 can be satisfied withoutchanging the directions of rubbing treatment in the two sections.

To mass-produce the liquid crystal displays, the most preferable opticaldesign of the liquid crystal is such that monotonously increases ordecreases the display brightness (reflectance or transmittance) inresponse to a driving voltage applied to the liquid crystal layer 1between its upper and lower limits.

When the above driving conditions are concerned, the simplest opticaldesign of the liquid crystal layer 1 is the one such that can attainelectro-optical characteristics which allow the display control, underwhich the display brightness monotonously increases or decreases whenthe liquid crystal aligned substantially perpendicular to the displaysurface is re-aligned to be substantially parallel to the displaysurface and vice versa.

In particular, when the parallel aligning alignment film is used toalign the liquid crystal in parallel with the display surface when novoltage is applied, there are specific conditions suitable for thereflection display; on the other hand, there are specific conditionssuitable for the transmission display as well. Thus, these conditionswere computed by the Jones matrix method to find optimal twist angles.

The result of the above computation was that, to obtain satisfactoryreflection display, the twist angle must be set to a range between 0 and100 inclusive.

To be more specific, the inventors of the present invention discoveredthat, if satisfactory reflection display is to be shown by means of theliquid crystal layer 1, the liquid crystal layer 1 must have an opticalproperty to convert the circularly polarized light to the linearlypolarized light efficiently when the liquid crystal is aligned to effectthe polarization converting function (when the parallel aligningalignment film is used, the liquid crystal is aligned substantially inthe same manner when no voltage is applied). To evaluate the abovefunction, the reflectance when the circularly polarized light enters theliquid crystal layer 1 was computed by the above-specified computationmethod. The reflectance computed herein is the reflectance of the lightthat enters the liquid crystal cell 200 in order of the polarizationplate 14, phase difference compensation plate 16 for imparting a phasedifference of 90 to the light, liquid crystal layer 1, and reflectionfilm 8, and then exits from the liquid crystal cell 200 in reversedorder.

Then, it turned out that when the twist angle is in a range between 0and 70 inclusive, the circularly polarized light can be converted to thelinearly polarized light perfectly by adjusting the product (n d) of adifference of refractive index (n) of the liquid crystal in the liquidcrystal layer 1 and a thickness (d) thereof for each twist angle of theliquid crystal layer 1. Also, the inventors of the present inventiondiscovered that when the twist angle is in a range between 70 exclusiveand 100 inclusive, although the circularly polarized light can not beconverted to the linearly polarized light perfectly, the resultingdisplay is satisfactorily. Thus, satisfactory reflectance can beobtained with light having a particular wavelength by adjusting n d ofthe liquid crystal layer 1 for each twist angle: the reflectance is 97%at the twist angle of 80, 83% at 90, and 72% at 100, when the maximumreflectance of the light having a visible wavelength at the twist angleup to 70 is scaled as 100%. However, if the twist angle exceeds 100, thecircularly polarized light can not be converted to the linearlypolarized light because the reflectance is reduced to 54% and 37% at thetwist angles of 110 and 120, respectively. In short, it is necessary toset the twist angle of the liquid crystal layer 1 to a range between 0and 100 inclusive in the reflection display section 9.

In the above explanation, the circularly polarized light was used forthe computation to evaluate the polarization converting function of theliquid crystal layer 1 in the reflection display section 9. However, inthe actual display, the incident light on the liquid crystal layer 1 inthe reflection display section 9 is not necessarily the circularlypolarized light, and satisfactory display can also be obtained in thereflection display section 9 if the linearly polarized light enters theabove-designed liquid crystal layer 1 instead.

On the other hand, to obtain the satisfactory display in thetransmission display section 10, the liquid crystal must be alignedeither at a small twist angle (in a range between 0 and 40 inclusive) ora large twist angle (in a range between 60 and 110 inclusive)

The polarization converting function necessary to obtain satisfactorydisplay in the transmission display section 10 must satisfy two types ofconditions: one is a basic optical function (first conditions), and theother is a practical optical function (second conditions) which isdetermined by a relation between the basic optical function (firstconditions) and the reflection display section 9.

The reason why is as follows. For example, to satisfy the firstconditions when the liquid crystal is aligned to effect the polarizationconverting function (when the parallel aligning alignment film is used,the liquid crystal is aligned substantially in the same manner when novoltage is applied), the liquid crystal layer 1 in the transmissiondisplay section 10 must efficiently convert particular polarized lightto another polarized light that is orthogonal to that particularpolarized light. To be more specific, in case that the particularpolarized light is the linearly polarized light, it is converted toanother linearly polarized light with which their respective planescontaining light oscillating electric fields intersect at right angles;in case that the particular polarized light is the circularly polarizedlight, it is converted to another circularly polarized light having aninverse rotation direction; and in case that the particular polarizedlight is elliptically polarized light in a specific state, it isconverted to another elliptically polarized light having an inverserotation direction and the same ellipticity while their major axisorientations intersecting at right angles.

Thus, the inventors of the present invention calculated the polarizationconverting function by the above-specified method (Jones matrix method)to evaluate the above function as the indispensable properties of thetransmission display section 10, and discovered that the twist angle isnot especially limited.

The second conditions become necessary due to a common optical film(polarization plate 14 and phase difference compensation plate 16) usedin both the reflection display section 9 and transmission displaysection 10 on the display front surface. The optical film on the frontsurface used both in the reflection display section 9 and transmissiondisplay section 10 is designed to show satisfactory reflection display.Another optical film set on a back surface of the display can be set tothe opposite surface of the liquid crystal display from the displaysurface, and it is preferable to provide the same at a direction suchthat realizes satisfactory display in the reflection display section 10together with the polarization plate 14 and phase differencecompensation plate 16 (serving as the optical film on the display frontsurface), and the liquid crystal layer 1 in the transmission displaysection 10 region. To do so, it is important that the polarizationconverting function of the liquid crystal layer 1 in the transmissiondisplay section 10 not only satisfies the first conditions, but alsoconverts the circularly polarized light to another circularly polarizedlight with a reversed rotation direction, or the incident linearlypolarized light to another polarized light intersecting at right angleswith the incident linearly polarized light in a satisfactory manner.

The luminance of the light, which will be converted from circularlypolarized light to a reversed rotation direction when it passes throughthe liquid crystal layer 1 in the form of circularly polarized light,was found by the above computation method to evaluate specificconditions satisfying the second conditions for the liquid crystal layer1 in the transmission display section 10. The transmittance computedherein is the transmittance of the light that sequentially passesthrough the polarization plate 15 (serving as a first polarizationplate), phase difference compensation plate 17 (serving as a first phasedifference compensation plate for imparting the phase difference of 90to the light), liquid crystal layer 1, phase difference compensationplate 16 (serving as a second phase difference compensation plate havingthe slow axis intersecting at right angles with a slow axis of the firstphase difference compensation plate for imparting the phase differenceof 90 to the light), and polarization plate 14 (serving as a secondpolarization plate that intersects at right angles with the firstpolarization plate).

Then, the inventors of the present invention discovered that circularlypolarized light can be converted to another circularly polarized lightwith a reversed rotation direction in a satisfactory manner when thetwist angle is in a range between 0 and 40 inclusive by adjusting n d ofthe liquid crystal layer 1 for each twist angle. More specifically, thetransmittance decreases with an increasing twist angle when thepolarization converting function that converts circularly polarizedlight to another circularly polarized light with an inverse rotationdirection is evaluated in the form of transmittance: the transmittanceat the twist angle of 30 is 88.6%, and is 80.8%, 72.0%, and 62.4% at thetwist angles of 40, 50, and 60, respectively, when the transmittance ofthe light having a visible wavelength at the twist angle of 0 is scaledas 100%. Consequently, the inventors of the present invention achievedthe conclusion that it is appropriate to set the upper limit of thetwist angle at approximately 40.

On the other hand, in setting twist angle in the transmission displaysection 10 which is able to efficiently convert linearly polarized lightto another linearly polarized light that intersects at the right angleswith the incident polarized light, satisfactory transmittance can beobtained efficiently at an arbitrary twist angle of 0 or above if thewavelength of the light is limited to one specific wavelength. However,to obtain high transmittance with visible light in a broad range ofwavelength, the twist angle must be set to an optimal value. Morespecifically, a band-width of a wavelength range, in which thetransmittance of 90% or above can be attained, is found by omitting theupper and lower limits of the wavelength when n d of the liquid crystallayer 1 is adjusted by changing the twist angel in such a manner thatthe transmittance achieves the maximum of 100% at a wavelength of 550nm, which is the wavelength at the center of the visible wavelengthrange. The transmittance computed herein is the transmittance of thelight that passes through the polarization plate 15 as the firstpolarization plate, liquid crystal layer 1, and polarization plate 14 asthe second polarization plate that intersects at right angles with thefirst polarization plate, during which the liquid crystal at the centerof the liquid crystal layer 1 in its layer thickness is aligned to forman angle of 45 with respect to the transmission axes of the polarizationplates 14 and 15.

Then it turned out that the band-width (range of wavelength) is 230 nmat the twist angle of 0, 235 nm at 10, 240 nm at 20, 245 nm at 30, 250nm at 40, 255 nm at 50, 265 nm at 60, 280 nm at 70, 310 nm at 80, 330 nmat 90, 305 nm at 100, 255 nm at 110, and 210 nm at 120.

In view of the foregoing, it is understood that when the twist angle isin a range between 60 and 110 inclusive, high transmittance can beattained in a broad range of wavelength (wavelength width), and thepolarization converting function is effected in a satisfactory manner,thereby realizing satisfactory display. Thus, the twist angle of theliquid crystal in the transmission display section 10 which satisfiesthe second conditions is limited to a range between 0 and 40 inclusiveor a range between 60 and 110 inclusive, due to the polarizationconverting function effected on circularly polarized light or linearlypolarized light.

As has been discussed, it turned out that satisfactory display can beobtained when the twist angle of liquid crystal layer 1 is in a rangebetween 0 and 100 inclusive in the reflection display section 9, and ina range between 0 and 40 inclusive or in a range between 60 and 110inclusive in the transmission display section 10.

Of all the examples explained below, when the twist angle of the liquidcrystal layer 1 is equal in the reflection display section 9 andtransmission display section 10 (Examples 2 through 9 and 11), Example11 is a typical case using the circularly polarized light at the twistangle of 0 (the liquid crystal is aligned perpendicular to the displaysurface); Example 3 is a typical case using the linearly polarized lightat the twist angle of 0 (the liquid crystal display is arranged to showsatisfactory light display by using the phase difference compensationplate); and Example 5 is a typical case using the linearly polarizedlight at the twist angle of approximately 70 (the liquid crystal displayis arranged to show satisfactory light display by using the phasedifference compensation plate).

Thus, the twist angle of the liquid crystal layer 1 to realizesatisfactory display on both the reflection display 9 and transmissiondisplay 10 is in a range between 0 and 40 inclusive or in a rangebetween 60 and 100 inclusive.

In the above explanation, the twist angle is indicated by positivedegrees. However, it should be appreciated that the same explanation canbe applied if the twist angle is indicated by negative degrees of thesame absolute value (the twist direction is reversed in this case).

In any case, when a small twist angle is set, a change of thepolarization state is expressed as a function of the product (n d) of adifference of refractive index (n) and a thickness (d) of the liquidcrystal layer, and moreover, the incident light passes through theliquid crystal layer 1 and returns through the same in the reflectiondisplay section 9 while the incident light passes through the liquidcrystal layer 1 only once in the transmission display section 10.Therefore, it is preferable to make the liquid crystal layer thicker inthe transmission display section 10 than in the reflection displaysection.

It should be appreciated that normal optical rotatory polarization usedin the TN liquid crystal display can be used for the light display anddark display exploiting the aforementioned polarization convertingfunction, because, in case that the TN liquid crystal display has a thinliquid crystal layer 1, the optical rotatory polarization and a changein the polarization state caused by the retardation can not bedistinguished and elliptically polarized light is generally used for thedisplay. The polarization converting function of the present inventionincludes the modulation of the luminance of the transmitted light usingthe above optical rotatory polarization.

Further, as has been described above, in the above polarizationconverting function, the change of the director configuration of theliquid crystal which can change the polarization state includes: thecontrol of the director configuration of the liquid crystal to beparallel or perpendicular to the substrates 4 and 5; as in the surfacestabilized ferroelectric liquid crystal or anti-ferroelectric liquidcrystal, the change of the director direction alone while keeping thedirector direction substantially in parallel with the substrates 4 and5; and, using nematic liquid crystal, the change of the directordirection of the liquid crystal, while keeping the director direction ina plane parallel to the display surface, by changing the electrodestructure.

In the above liquid crystal display, the position (laminationorientation) of the polarization plates 14 and 15 can be set in anysuitable manner. For example, if the polarization plate 14 is set to aposition corresponding to the position of the reflection display section9, then the polarization plate 15 is set to a position corresponding tothe polarization plate 14, because the polarization plate 14 naturallyaffects the display light passing through the transmission displaysection 10 as well.

As has been explained, in case of using the non-twisted directorconfiguration of the liquid crystal, when the reflection display section9 shows, for example, the dark display, so does the transmission displaysection 10. However, for example, when only the polarization plate 15 isturned 90 while leaving the orientation of the polarization plate 14intact, the display is inverted between in the reflection displaysection and in the transmission display section 10, thereby making itimpossible to obtain satisfactory display. Thus, to prevent suchunwanted inversion of the display, the polarization plate 15 is returnedto the initial position, or the electrodes are provided to thereflection display section 9 and transmission display section 10individually to invert the electrical driving itself either in thereflection display section 9 or transmission display section 10 alone,so that both the display sections shows either the light or dark displaysimultaneously.

Next, the display principle in the reflection display section 9 andtransmission display section 10 of the liquid crystal display of FIG. 4will be explained in further detail.

To begin with, the display principle in the reflection display section 9will be explained. Assume, for ease of explanation, that the phasedifference compensation plates 16 and 17 are omitted and the directorconfiguration of the liquid crystal in the liquid crystal layer 1 is nottwisted in the reflection display section 9 b nor transmission displaysection 10 b. Also, assume that the thicknesses of the liquid crystallayer 1 in the reflection display section 9 and transmission displaysection 10 are adjusted in such a manner that the reflection displaysection 9 b and transmission display section 10 b respectively causephase differences of ¼ wavelength and ½ wavelength when the light havinga wavelength of 550 nm passes through the liquid crystal layer 1 onlyonce. Also, the liquid crystal composition has positive dielectricconstant anisotropy and the liquid crystal is aligned substantially inparallel with the substrates 4 and 5 when no voltage is applied, and thealignment orientation and the absorption axis orientation of thepolarization plate 14 form 45 within display plane.

In this case, the director configuration of the liquid crystal in thereflection display section 9 and transmission display section 10 when novoltage is applied is the director configuration of the liquid crystalshown in the reflection display section 9 b and transmission displaysection 10 b, and upon application of a voltage, the directorconfiguration of the liquid crystal in the reflection display section 9and transmission display section 10 is changed to the one shown in thereflection display section 9 a and transmission display section 10 a.

In the reflection display section 9 b, the product (n d) of a differenceof refractive index (n) of the liquid crystal composition and athickness (d) of the liquid crystal layer satisfies the ¼ wavelengthcondition. Thus, the ambient light is converted to linearly polarizedlight by the polarization plate 14 when it enters the liquid crystallayer 1, and converted further to circularly polarized light by theretardation of the liquid crystal layer 1 before it reaches thereflection film 8. The incident light inverts its direction ofpropagation on the reflection film 8, while the circularly polarizedlight inverts its direction of propagation alone while keeping therotational direction of the oscillating electric field. Hence, thecircularly polarized light is converted to circularly polarized lightorthogonal to the polarized light at the time of incidence, in otherwords, circularly polarized light is inverted from right to left. Then,the resulting circularly polarized light is converted to linearlypolarized light parallel to the absorption axis orientation of thepolarization plate 14 after it has passed through the liquid crystallayer 1 in the reflection display section 9 b again, and absorbed by thepolarization plate 14, thereby showing the dark display.

Here, in the transmission display section 10 b, the product (n d) of adifference of refractive index (n) of the liquid crystal composition anda thickness (d) of the liquid crystal layer satisfies the ½ wavelengthcondition. Thus, the liquid crystal layer 1 has a function of convertingthe orientation of the oscillation plane of the linearly polarizedincident light symmetrically with respect to a line along the alignmentdirection of the liquid crystal. Thus, the orientation of the absorptionaxis of the polarization plate 15 on the light incident side in thetransmission display section 10 b is determined to become parallel tothe transmission axis orientation of the polarization plates 14 and 15,so that the light passing through the polarization plate 14 is absorbedtherein by the aforementioned function of the liquid crystal layer 1,thereby showing the dark display.

As mentioned above, it has been discovered that, when the polarizationplates 14 and 15 are provided in such a manner that their transmissionaxis orientations are parallel to each other, and the alignmentdirection of the liquid crystal and the transmission axis orientationforms angle of 45 in the above manner, both the reflection displaysection 9 b and transmission display section 10 b show the dark display.

Next, the following will explain a function when the directorconfiguration of the liquid crystal is changed to be substantiallyperpendicular to the display surface as shown in the reflection displaysection 9 a and transmission display section 10 a by supplying apotential difference between the electrodes 6 and 7 from the state whereno voltage is applied (initial director configuration of the liquidcrystal) as shown in the reflection display section 9 b and transmissiondisplay section 10 b.

In this case, in the reflection display section 9 a, the ambient lightis converted to linearly polarized light by the polarization plate 14,and since the liquid crystal layer 1 does not have the retardation forthe linearly polarized light, the incident light reaches the reflectionfilm 8 while maintaining its polarization state. After the direction ofpropagation is inverted, the light passes through the liquid crystallayer 1 again, and exits through the polarization plate 14 whilemaintaining its direction of polarization which intersect at rightangles with the absorption axis orientation of the polarization plate14.

Also, like in the reflection display section 9 a, in the transmissiondisplay section 10 a, the incident light is converted to linearlypolarized light by the polarization plate 15, and passes through thepolarization plate 14 while keeping its polarization state substantiallythe same.

When using the above polarization converting function exploiting theoptical anisotropy for the display, an amount of the polarizationconverting function is determined, for example, when the liquid crystalis aligned in parallel with the display surface and no voltage isapplied to the liquid crystal layer 1, by an angle of twist of thedirector configuration of the liquid crystal layer 1, and the product (nd) of a thickness (d) of the liquid crystal layer and a difference ofrefractive index (n) of the liquid crystal composition. Thus, providinga thicker liquid crystal layer in the transmission display section 10than in the reflection display section 9, as in the present invention,is effective for a liquid crystal display using both the transmittedlight and reflected light for the display to obtain satisfactorybrightness and contrast ratio for the display in both the reflectiondisplay section 9 and transmission display section 10. The angle oftwist may be different in the reflection display section 9 andtransmission display section 10.

When the liquid crystal display includes the phase differencecompensation plates 16 and 17, satisfactory brightness and contrastratio can be attained in a reliable manner with respect to light havingmore than one wavelength in the range of visible light, thereby makingit possible to realize even more satisfactory display.

Also, if the liquid crystal composition and director configuration ofthe liquid crystal layer 1 are identical to one in the aboveexplanation, a change in the display can be inverted by the function ofthe phase difference compensation plates 16 and 17. More specifically,when ¼ wavelength plates are used as the phase difference compensationplates 16 and 17, in the reflection display section 9 b, the ambientlight is converted to circularly polarized light by the phase differencecompensation plate 16 upon incidence on the liquid crystal layer 1, andconverted further to linearly polarized light by the polarizationconverting function exploiting the optical anisotropy of the liquidcrystal layer 1 before it reaches the reflection film 8. Then, after itsdirection of propagation is inverted at the reflection film 8, thelinearly polarized light becomes the transmission components of thepolarization plate 14 and exits through the same, thereby showing thelight display. On the other hand, when the director configuration of theliquid crystal is changed as shown in the reflection display section 9a, the ambient light reaches the reflection film 8 as the circularlypolarized light, thereby showing the dark display.

The foregoing explained a case where the dark display changes to thelight display with an increasing potential difference between theelectrodes 6 and 7 was explained. However, it should be appreciated sucha change in display is not limited to the above disclosure. For example,as has been explained, the display can be inverted by using a liquidcrystal composition having negative dielectric constant anisotropy inthe liquid crystal layer 1, or giving the liquid crystal verticalalignment in the initial stage.

Here, setting the initial director configuration of the liquid crystalperpendicular to the display surface can offer technical characteristicssuch that the polarization converting function of the initial directorconfiguration is not greatly affected by a manufacturing accuracy of thethickness of the liquid crystal layer. Thus, taking advantage of theabove characteristics it is highly productive to assign the initialdirector configuration to black display, thereby stabilizing blackdisplay, which affects display quality considerably. In particular, todo so, black must be shown at a state where the polarization convertingfunction of the perpendicularly aligned liquid crystal layer 1 is almostcompletely lost, and the phase difference compensation plate 16 musthave satisfactory circularly polarizing function. In short, it isimportant that the phase difference compensation plate 16 is arranged insuch a manner as to convert the incident light to circularly polarizedlight in a wavelength range as broad as possible.

When the phase difference compensation plates 16 and 17 are provided tohave their respective slow axis orientations intersecting at rightangles and the polarization plates 14 and 15 are provided to have theirrespective absorption axis orientations intersecting at right angles,the transmission display section 10 shows the light display with thedirector configuration of the liquid crystal shown in the transmissiondisplay section 10 b and the dark display with the directorconfiguration of the liquid crystal shown in the transmission displaysection 10 a.

In the liquid crystal display of the present invention, whether theliquid crystal layer 1 is aligned in parallel with or perpendicular tothe display surface, in case that the thicknesses of the liquid crystallayer are different in the reflection display section 9 and transmissiondisplay section 10, to obtain satisfactory brightness and contrast ratioboth in the reflection display section 9 and transmission displaysection 10, when the reflection display section 9 shows the display byletting the incident light from the display surface side pass throughthe liquid crystal layer 1 and go out to the display surface sidethrough the liquid crystal layer 1 again, and the transmission displaysection 10 shows the display by letting the incident light from behind(back light 13 side) pass through the liquid crystal layer 1 only onceand go out to the display surface side, it is very effective to make theliquid crystal layer thicker in the transmission display section 10 thanin the reflection display section 9, and therefore, to satisfy theaforementioned conditions.

In the following, of all the liquid crystal displays of the presentembodiment, those using the change of the polarization state caused bythe polarization converting function of the liquid crystal layer 1 withthe polarization plates 14 and 15 will be explained by way of examplesand comparative examples with reference to FIGS. 4 through 8 forpurposes of explanation only, without any intention as a definition ofthe limits of the invention.

Examples 2-4

In each of Examples 2 through 4, liquid crystal cells for filling areassembled in the same manner as Example 1. Here, the thicknesses (d) ofthe liquid crystal layer in the transmission display section 10 andreflection display section 9 are 7.5 m and 4.5 m, respectively. In otherwords, in Examples 2 through 4, the liquid crystal layer 1 is madethicker in the transmission display section 10 than in the reflectiondisplay section 9 by patterning the insulation film 11 in such a manneras to leave no photosensitive resin in the transmission display sectionand form a 3 m-thick layer of the photosensitive resin in the reflectiondisplay section 9. However, in Examples 2 through 4, as shown in FIG. 4,the electrode pattern is formed in such a manner that the electrode 7 ofthe reflection display section 9 and the electrode 7 of the transmissiondisplay section 10 are electrically isolated, so that a voltage isapplied to each separately from outside the liquid crystal cell.

Further, in Examples 2 through 4, the liquid crystal layer 1 is producedby filling liquid crystal composition with no chiral dopant, havingpositive dielectric constant anisotropy and a difference of refractiveindex (n) of 0.065 by means of vacuum injection.

Then, the liquid crystal displays are assembled by laminating the phasedifference compensation plates 16 and 17 and polarization plates 14 and15 to the outside of the respective electrode substrates of the liquidcrystal cell produced in the above manner. Here, the phase differencecompensation plate 17 is composed of two phase difference compensationplates in Examples 2 through 4, while the phase difference compensationplate 16 is composed of two phase difference compensation plates inExamples 2 and 4, and a single phase difference compensation plate inExample 3. The lamination orientation of the phase differencecompensation plates 16 and 17 and polarization plates 14 and 15 isdetermined correspondingly to the alignment direction (alignmentorientation) of the liquid crystal.

In Example 2, homogeneous alignment is used as the directorconfiguration of the liquid crystal, and the NB (Normally Black) mode isused for the display mode. In Example 3, the homogenous alignment isused as the director configuration of the liquid crystal, and the NW(Normally White) mode is used for the display mode. In Example 4, acombination of these modes are used (the NB mode is used for thereflection display, and the NW mode is used for the transmissiondisplay).

In Examples 2 through 4, parallel aligning alignment films are used asthe alignment films 2 and 3, so that the liquid crystal is aligned inparallel with the display surface when no voltage is applied to theliquid crystal layer 1, and the alignment treatment is applied to thesealignment films 2 and 3 to form a crossed rubbing angle of 180.

Here, the crossed rubbing angle is defined, as shown in FIG. 5, in theliquid crystal cell for filling composed of a pair of electrodesubstrates sandwiching the liquid crystal layer 1, as an angle of therubbing direction; Y of the alignment treatment orientation of thealignment film 3 (the alignment film 3 on the substrate 5 side) on theelectrode substrate in a let direction with respect to the rubbingdirection X of the alignment treatment orientation of the otheralignment film 2 (alignment film 2 on the substrate 4 side) on theelectrode substrate on the viewer's side.

The director configuration of the liquid crystal molecules in the liquidcrystal layer 1 sandwiched by the alignment treated alignment films 2and 3 is determined by the alignment properties of the alignment films 2and 3, a concentration of the chiral dopant for imparting a naturaltwist to the liquid crystal, and the crossed rubbing angle, when neitherelectric field nor magnetic field exists.

When the crossed rubbing angle is 180, the liquid crystal compositionaligns itself without twisting when no chiral dopant is added. When thechiral dopant induces a left-handed twist, the director configuration ofthe liquid crystal remains intact until a predetermined amount of thechiral dopant is added, and when an amount added exceeds thepredetermined amount, the liquid crystal twists 180 to the left (180left twist alignment), and with a further increasing amount of thechiral dopant, the liquid crystal twists by an angle of an integralmultiple of 180.

Thus, in the present embodiment, given x as the rubbing orientation X ofthe alignment film 2 provided on the electrode substrate above theliquid crystal layer 1, then the alignment orientation of the liquidcrystal on the alignment film 3 realized by the crossed rubbing angle(180) is x when no chiral dopant is added, and the alignment orientationis (180+x) when the liquid crystal is twisted 180 to the left betweenthe electrode substrates above and beneath the liquid crystal layer 1with an increasing amount of the chiral dopant.

In case that the nematic liquid crystal having positive dielectricconstant anisotropy and no chiral dopant is used when the alignmentfilms 2 and 3 are the parallel aligning alignment films that align theliquid crystal in parallel with their film surfaces, when no voltage isapplied, the liquid crystal molecules take an director configurationsubstantially parallel to the electrode substrates sandwiching theliquid crystal layer 1 above and beneath with no twist (that is, thehomogenous alignment), and upon voltage application, the alignmentstarts to change from the central portion of the liquid crystal layer 1in the layer thickness direction.

The optical of the polarization plates 14 and 15, phase differencecompensation plates 16 and 17, and the liquid crystal layer 1 (that is,the lamination orientation of the polarization plates 14 and 15, andphase difference compensation plates 16 and 17, and the alignmentorientation of the liquid crystal) in the liquid crystal displays inExamples 2 through 4 is set forth in Table 1 below for ready comparisonwith reference to a common orientation in any example.

The optical set forth in Table 1 is the position of each optical elementon the display surface when the viewer observes the display surface, andwhen the phase difference compensation plate 16 or 17 is composed ofmore than one phase difference compensation plate, each phase differencecompensation plate forming the phase difference compensation plate 16 or17 is set forth in accordance with the actual position from the viewer'sside.

Since the liquid crystal layer 1 is aligned without any twist, thealignment orientation (alignment orientation of the major axis of theliquid crystal molecules) of the entire liquid crystal layer 1 when novoltage is applied is set forth in Table 1 below, and this alignmentorientation is the orientation of the rubbing treatment applied to thealignment film 2 on the substrate 4 side.

Each orientation is expressed in degrees from the reference orientationset arbitrarily on the display surface, and the retardation (product ofa difference of in-plane refractive index and a thickness of the phasedifference compensation plate) of each phase difference compensationplate is expressed in nm with respect to a beam of monochrome lighthaving the wavelength of 550 nm.

TABLE 1 EXAMPLE 2 3 4 PLATE 14 TRANSMISSION AXIS ORIENTATION (°) 0 0 0PLATE 16 PLATE SLOW AXIS ORIENTATION (°) 15 15 15 RETARDATION (nm) 270270 270 PLATE SLOW AXIS ORIENTATION (°) 165 — 165 RETARDATION (nm) 135 —135 LC LAYER 1 ALIGNMENT ORIENTATION (°) 75 75 75 PLATE 17 PLATE SLOWAXIS ORIENTATION (°) 165 165 165 RETARDATION (nm) 70 220 90 PLATE SLOWAXIS ORIENTATION (°) 135 135 105 RETARDATION (nm) 270 270 270 PLATE 15TRANSMISSION AXIS ORIENTATION (°) 60 60 90 PLATES 14 × 15: POLARIZATIONPLATES PLATES 16 × 17: PHASE DIFFERENCE COMPENSATION PLATES

The display characteristics of the liquid crystal displays assembled inExamples 2 through 4 are graphed in FIGS. 6 through 8, respectively.These display characteristics were measured in the same manner asExample 1, and in these drawings, the horizontal axis represents a rootmean square value of the applied voltage, and the vertical axisrepresents the brightness (reflectance or transmittance). Here, thetransmittance of the transmission display section 10 when thepolarization plates 14 and 15 are not provided is scaled as 100%, andthe reflectance of the reflection display section 9 before thepolarization plate 14 is provided is scaled as 100%.

In FIG. 6, a curve 211 represents the voltage dependence of thereflectance of the reflection display section 9 versus a voltage acrossthe electrodes 6 and 7, and a curve 212 represents the voltagedependence of the transmittance of the transmission display section 10versus a voltage across the electrodes 6 and 7 in the liquid crystaldisplay assembled in Example 2.

FIG. 6 reveals that, in Example 2, while the applied voltage is in arange between 1V and 2V, both the reflectance and transmittance increasewith an increasing applied voltage. That is, when the applied voltage is1V, the reflectance of the reflection display section 9 and thetransmittance of the transmission display section 10 are 3% and 2%,respectively, and when the applied voltage is increased to 2V, bothincrease to 40%.

In FIG. 7, a curve 221 represents the voltage dependence of thereflectance of the reflection display section 9 versus a voltage acrossthe electrodes 6 and 7, and a curve 222 represents the voltagedependence of the transmittance of the transmission display section 10versus a voltage across the electrodes 6 and 7 in the liquid crystaldisplay assembled in Example 3.

FIG. 7 reveals that, in Example 3, while the applied voltage is in arange between 1V and 2V, both the reflection and transmittance decreasewith an increasing applied voltage. That is, when the applied voltage is1V, both the reflectance of the reflection display section 9 and thetransmittance of the transmission display section 10 are 40%, and whenthe applied voltage is increased to 2V, both decrease to 3% and 2%,respectively.

In FIG. 8, a curve 231 represents the voltage dependence of thereflectance of the reflection display section 9 versus a voltage acrossthe electrodes 6 and 7, and a curve 232 represents the voltagedependence of the transmittance of the transmission display section 10versus a voltage across the electrodes 6 and 7 in the liquid crystaldisplay assembled in Example 4.

FIG. 8 reveals that, in Example 4, while the applied voltage is in arange between 1V and 2V, the reflectance increases while thetransmittance decreases with an increasing applied voltage. That is,when the applied voltage is 1V, the reflectance of the reflectiondisplay section 9 and the transmittance of the transmission displaysection 10 are 3% and 40%, respectively, and when the applied voltage isincreased to 2V, the reflectance of the reflection display section 9increases to 40%, while the transmittance of the transmission displaysection 10 decreases to 2%.

As has been explained, in all the liquid crystal displays assembled inExamples 2 through 4, the transmittance and reflectance change inresponse to a change in the applied voltage, and each can show both thereflection display and transmission display.

Further, the changes were checked visually. Then, in Examples 2 and 3,it was confirmed that the changes between the light display and darkdisplay is equal and the display was not inverted (from light to darkand vice versa) in the reflection display section 9 and transmissiondisplay section 10. This is because the display is shown by applying thesame voltage to the electrode 7 of the reflection display section 9 andthe electrode 7 of the transmission display section 10 to keep theapplied voltage to the liquid crystal layer 1 equal in the reflectiondisplay section 9 and transmission display section 10 by means of theelectrodes 6 and 7. In addition, no change in the content of the displaywas observed when the luminance of the ambient light was changed duringthe observation. In other words, when the reflection display section 9shows the dark display, so does the transmission display section 10, andwhen the reflection display section 9 shows the light display, so doesthe transmission display section 10. For this reason, even when thereflection display section 9 and transmission display section 10 aredriven by the same electrode 7 as is shown in FIG. 1, the display is notinverted.

By contrast, in Example 4, when the voltage is applied in the samemanner as Examples 2 and 3, that is, when a voltage of 1V is applied,the transmission display section 10 shows the light display while thereflection display section 9 shows the dark display. Then, when avoltage of 2V is applied, the transmission display section 10 shows thedark display while the reflection display section 9 shows the lightdisplay. Hence, the displays are inverted in the reflection displaysection 9 and transmission display section 10. Thus, when the display isshown under the circumstance where the ambient light is weak, and thedisplay is shown by the reflection display by brightening the ambientlight when the user is mainly observing the transmission display section10, the display is inverted (from light to dark and vice versa), and asa consequence, it becomes difficult to see the display content. Thus,when, as in Example 4, the same voltage was applied to the electrode 7in the reflection display section 9 and the electrode 7 in thetransmission display section 10, it was confirmed that the displays ofthe reflection display section 9 and transmission display section 10were inverted considerably in a combination mode of the NB and NW,thereby deteriorating the visibility.

However, in Example 4, the problem of such unwanted inversion of thedark display and light display can be resolved and a display state assatisfactory as those in Examples 2 and 3 can be obtained by applyingdifferent voltages to the electrode 7 in the reflection display section9 and the electrode 7 in the transmission display section 10, so thatwhen the reflection display section 9 shows the light display, so doesthe transmission display section 10, and when the reflection displaysection 9 shows the dark display, so does the transmission displaysection 10. More specifically, by means of the electrodes 6 and 7(alignment mechanism), when a voltage of 1V is applied to the reflectiondisplay section 9 to let the same show the dark display, a voltage of 2Vis applied to the transmission display section 10 to let the same showthe dark display too, but when a voltage of 2V is applied to thereflection display section 9 to let the same show the light display, avoltage of 1V is applied to the transmission display section 10 to letthe same show the light display too.

In view of the foregoing, the liquid crystal display in any of Examples2 through 4 can attain satisfactory brightness and contrast ratio forthe light display in both the reflection display section 9 andtransmission display section 10. Moreover, the liquid crystal display inany of Examples 2 through 4 can match the dark/light display in thereflection display section 9 and transmission display section 10,thereby realizing display with excellent visibility. Further, the liquidcrystal display in any of Examples 2 through 4 has a higher contrastratio in the transmission display section 10 than in the reflectiondisplay section 9. Consequently, the display quality can be furtherimproved and more satisfactory display can be shown.

Next, of all the liquid crystal displays of the present embodiment, aliquid crystal display using the polarization converting function of theliquid crystal layer 1 effected by the twist alignment thereof will beexplained by way of examples and comparative examples with reference toFIGS. 9 and 10 for purposes of explanation only, without any intentionas a definition of the limits of the invention.

Example 5

In the present example, a liquid crystal cell for filling is assembledin the same manner as Example 1. Here, the thicknesses (d) of the liquidcrystal layer in the transmission display section 10 and reflectiondisplay section 9 are 7.5 m and 4.5 m, respectively. In other words, inthe present example too, the thickness of the liquid crystal layer ismade thicker in the transmission display section 10 than in thereflection display section 9 by patterning the insulation film 11 insuch a manner as to leave no photosensitive resin in the transmissiondisplay section 10 and form a 3 m-thick layer of the photosensitiveresin in the reflection display section 9.

However, in the present example, like in Examples 2 through 4 as shownin FIG. 4, the electrode pattern is formed in such a manner that theelectrode 7 of the reflection display section 9 and the electrode 7 ofthe transmission display section 10 are electrically isolated, so that avoltage is applied to each separately from outside the liquid crystalcell.

Further, the phase difference compensation plates 16 and 17 andpolarization plates 14 and 15 are laminated to the outside of therespective electrode substrates of the above liquid crystal cell. Here,the phase difference compensation plate 17 is composed of a single phasedifference compensation plate, while the phase difference compensationplate 16 is composed of two phase difference compensation plates. Thelamination orientation of the phase difference compensation plates 16and 17 and polarization plates 14 and 15 is determined correspondinglyto the alignment direction (alignment orientation) of the liquidcrystal.

In the present example, the liquid crystal display is assembled in sucha manner that the twist director configuration of the liquid crystallayer 1 (angle of twist of the director configuration of the liquidcrystal (twist angle)) is 70. More specifically, parallel aligningalignment films are used as the alignment films 2 and 3, so that thedirector configuration of the liquid crystal is parallel to the displaysurface when no voltage is applied, and the alignment treatment isapplied to these alignment films 2 and 3 by means of rubbing in such amanner as to form the crossed rubbing angle of 250. The crossed rubbingangle is defined as above. Then, the liquid crystal layer 1 is producedby using vacuum injection to full a space between the electrodesubstrates of the above liquid crystal cell with a liquid crystalcomposition having a difference of refractive index (n) of 0.065 andpositive dielectric constant anisotropy. The above alignment treatmentand the function of the chiral dopant added to the liquid crystalcomposition impart an angle of twist (twist angle) of 70 to the directorconfiguration of the liquid crystal. The liquid crystal layer 1 alignedin this manner starts to change its alignment upon application of thevoltage from the central portion thereof in the layer thicknessdirection.

The optical of the polarization plates 14 and 15, phase differencecompensation plates 16 and 17, and the liquid crystal layer 1 (that is,the lamination orientation of the polarization plates 14 and 15, andphase difference compensation plates 16 and 17, and the alignmentorientation of the liquid crystal) in the liquid crystal display of thepresent example is set forth in Table 2 below for ready comparison withreference to a common orientation.

Example 6

In the present example, like in Example 5, a liquid crystal cell forfilling is assembled in the same manner as Example 1. Here, thethicknesses (d) of the liquid crystal layer in the transmission displaysection 10 and reflection display section 9 are 7.5 m and 4.5 m,respectively. Also, as shown in FIG. 4, the electrode pattern is formedin such a manner that the electrode 7 of the reflection display section9 and the electrode 7 of the transmission display section 10 areelectrically isolated, so that a voltage is applied to each separatelyfrom outside the liquid crystal cell.

Further, the phase difference compensation plates 16 and 17 andpolarization plates 14 and 15 are laminated to the outside of therespective electrode substrates of the above liquid crystal cell. Here,each of the phase difference compensation plates 16 and 17 is composedof a single phase difference compensation plate. The laminationorientation of the phase difference compensation plates 16 and 17 andpolarization plates 14 and 15 is determined correspondingly to thealignment direction (alignment orientation) of the liquid crystal.

In the present example, the liquid crystal display is assembled in sucha manner that the twist director configuration of the liquid crystallayer 1 (twist angle) is 90. More specifically, parallel aligningalignment films are used as the alignment films 2 and 3, so that thedirector configuration of the liquid crystal becomes parallel to thedisplay surface when no voltage is applied, and the alignment treatmentis applied to these alignment films 2 and 3 by means of rubbing in sucha manner as to form the crossed rubbing angle of 270. The crossedrubbing angle is defined as above. Then, the liquid crystal layer 1 isproduced by filling the liquid crystal composition having a differenceof refractive index (n) of 0.065 and the positive dielectric constantanisotropy into a space between the electrode substrates of the liquidcrystal cell for filling by means of vacuum injection. The abovealignment treatment and the function of the chiral dopant added to theliquid crystal composition impart the angle of twist (twist angle) of 90to the director configuration of the liquid crystal. The liquid crystallayer 1 aligned in this manner starts to change its alignment uponapplication of the voltage from the central portion thereof in the layerthickness direction.

The optical of the polarization plates 14 and 15, phase differencecompensation plates 16 and 17, and the liquid crystal layer 1 (that is,the lamination orientation of the polarization plates 14 and 15, andphase difference compensation plates 16 and 17, and the alignmentorientation of the liquid crystal) in the liquid crystal display of thepresent example is set forth in Table 2 below for ready comparison witha reference to common orientation.

The optical set forth in Table 2 is the position of each optical elementon the display surface when the viewer observes the display surface, andwhen the phase difference compensation plate 16 or 17 is composed ofmore than one phase difference compensation plate, each phase differencecompensation plate forming the phase difference compensation plate 16 or17 is set forth in accordance with the actual position from the viewer'sside.

The alignment orientation of the liquid crystal layer 1 (the alignmentorientation of the major axis of the liquid crystal molecules) on thesubstrate 4 side is identical with the orientation of the rubbingtreatment applied to the alignment film 2 on the substrate 4, and on thesubstrate 5 side is identical with the orientation of the rubbingtreatment applied to the alignment film 3 on the substrate 5. Note that,however, when the alignment orientation of the liquid crystal touchingthe alignment film 2 is traced toward the alignment film 3, thealignment orientation is twisted 90 to the left. In case that thedirector configuration of the liquid crystal is traced in the abovemanner, on the assumption that the orientation of the rubbing treatmentapplied to the alignment film 2 is the alignment orientation on thesubstrate 4 side (hereinafter, referred to as the substrate 4 alignmentorientation), the rubbing orientation of the alignment film 3 isinverted by 180 from the orientation traced along the twist of thedirector configuration of the liquid crystal. In the following, thealignment orientation on the substrate 5 side (hereinafter, referred toas the substrate 5 alignment orientation) is defined as the directorconfiguration of the liquid crystal on the substrate 5 traced along thetwist of the director configuration of the liquid crystal from thesubstrate 4 alignment orientation.

Each orientation is expressed in degrees from the reference orientationset arbitrarily on the display surface, and the retardation of eachphase difference compensation plate is expressed in nm with respect to abeam of monochrome light having the wavelength of 550 nm.

TABLE 2 EXAMPLE 5 6 PLATE 14 TRANSMISSION AXIS ORIENTATION (°) 0 0 PLATE16 PLATE SLOW AXIS ORIENTATION (°) 18 12 RETARDATION (nm) 270 135 PLATESLOW AXIS ORIENTATION (°) 126 — RETARDATION (nm) 135 — LC LAYER 1SUBSTRATE 4 ALIGNMENT ORIENTATION (°) 16 −11 SUBSTRATE 5 ALIGNMENTORIENTATION (°) 86 79 PLATE 17 PLATE SLOW AXIS ORIENTATION (°) −4 135RETARDATION (nm) 260 260 PLATE 15 TRANSMISSION AXIS ORIENTATION (°) 15290 PLATES 14 × 15: POLARIZATION PLATES PLATES 16 × 17: PHASE DIFFERENCECOMPENSATION PLATES

The display characteristics of the liquid crystal displays assembled inExamples 5 and 6 are graphed in FIGS. 9 and 10, respectively. Thesedisplay characteristics were measured in the same manner as Example 1,and in each drawing, the horizontal axis represents a root mean squarevalue of the applied voltage, and the vertical axis represents thebrightness (reflectance or transmittance). Here, the transmittance ofthe transmission display section 10 when the polarization plates 14 and15 are not provided is scaled as 100%, and the reflectance of thereflection display section 9 before the polarization plate 14 isprovided is scaled as 100%.

In FIG. 9, a curve 241 represents the voltage dependence of thereflectance of the reflection display section 9 versus a voltage acrossthe electrodes 6 and 7, and a curve 242 represents the voltagedependence of the transmittance of the transmission display section 10versus a voltage across the electrodes 6 and 7 in the liquid crystaldisplay assembled in Example 5.

FIG. 9 reveals that, in Example 5, while the applied voltage is 1.2V orhigher, both the reflectance and transmittance increase with anincreasing applied voltage. That is, when the applied voltage is 1V, thereflectance of the reflection display section 9 and the transmittance ofthe transmission display section 10 are 3% and 2%, respectively, andwhen the applied voltage is increased to 4V, both increase to 41% and40%, respectively.

In FIG. 10, a curve 251 represents the voltage dependence of thereflectance of the reflection display section 9 versus a voltage acrossthe electrodes 6 and 7, and a curve 252 represents the voltagedependence of the transmittance of the transmission display section 10versus a voltage across the electrodes 6 and 7 in the liquid crystaldisplay assembled in Example 6.

FIG. 10 reveals that, in Example 6, like in Example 5, while the appliedvoltage is 1.2V or higher, both the reflectance and transmittanceincrease with an increasing applied voltage. That is, when the appliedvoltage is 1V, the reflectance of the reflection display section 9 andthe transmittance of the transmission display section 10 are 3% and 2%,respectively, and when the applied voltage is increased to 4V, bothincrease to 35% and 37%, respectively.

As has been explained, in each of the liquid crystal displays assembledin Examples 5 and 6, the transmittance and reflectance change inresponse to a change in the applied voltage, and each can show both thereflection display and transmission display.

Further, the changes were checked visually. Then, in Examples 5 and 6,it was confirmed that the changes between the light display and darkdisplay were equal and the display was not inverted (from light to darkand vice versa) in the reflection display section 9 and transmissiondisplay section 10, even when the display is shown by applying the samevoltage to the electrode 7 of the reflection display section 9 and theelectrode 7 of the transmission display section 10 to keep the appliedvoltage to the liquid crystal layer 1 equal in the reflection displaysection 9 and transmission display section 10 by the electrodes 6 and 7.In addition, a change in the content of the display is not observed whenthe luminance of the ambient light is changed during the observation. Inother words, when the reflection display section 9 shows the darkdisplay, so does the transmission display section 10, and when thereflection display section 9 shows the light display, so does thetransmission display section 10. For this reason, even when thereflection display section 9 and transmission display section 10 aredriven by the same electrode 7 as is shown in FIG. 1, the display is notinverted in Example 5 nor 6.

In view of the foregoing, the liquid crystal displays in Examples 5 and6 can attain satisfactory brightness and contrast ratio for the lightdisplay in both the reflection display section 9 and transmissiondisplay section 10. Moreover, the liquid crystal displays in Examples 5and 6 can match the dark/light display in the reflection display section9 and transmission display section 10, thereby realizing display withexcellent visibility. Further, the liquid crystal displays in Examples 5and 6 have a higher contrast ratio in the transmission display section10 than in the reflection display section 9. Consequently, the displayquality can be further improved and more satisfactory display can beshown.

Also, both the liquid crystal displays of Examples 5 and 6 have goodvisibility, and can show a high-resolution color display while usingboth the reflected light and transmitted light, but the liquid crystaldisplay of Example 6 is less expensive compared with its counterpart ofExample 5, because the former uses fewer phase difference compensationplates.

Explained in the present embodiment was the liquid crystal display whichcan show satisfactory reflection display and transmission display bychanging the thickness of the liquid crystal layer in the reflectiondisplay section and transmission display section. The following willexplain a liquid crystal display, which can show satisfactory reflectiondisplay and transmission display even though the thicknesses of theliquid crystal layer in the reflection display section and transmissiondisplay section are equal.

Embodiment 3

Explained in the present embodiment is a liquid crystal display whichhas the equal thickness of the liquid crystal layer in the reflectiondisplay section and transmission display section but can showsatisfactory reflection display and transmission display by changing thedirector configuration of the liquid crystal by applying differentvoltages to the reflection display section and transmission displaysection.

In the present embodiment, a liquid crystal display, which has thepolarization plates 14 and 15 of Embodiment 2 and the equal thickness ofthe liquid crystal layer in the reflection display section andtransmission display section and uses the retardation of the liquidcrystal layer 1 for the display, will be explained by way of examplesand comparative examples with reference to FIGS. 4 and 11 through 16 forpurposes of explanation only, without any intention as a definition ofthe limits of the invention.

Hereinafter, like components are labeled with like reference numeralswith respect to Embodiments 1 and 2, and, for ease of explanation, thedescription of these components is not repeated here. Also, thearrangement of the entire liquid crystal display of the presentembodiment is identical with its counterpart of Embodiment 2 except thatthe thickness of the liquid crystal layer is equal in the reflectiondisplay section 9 and transmission display section 10, and thedescription of which is not repeated either for ease of explanation.

To give the liquid crystal layer 1 equal thicknesses in the reflectiondisplay section 9 and transmission display section 10 like in thepresent embodiment, the insulation film 11 is omitted and the electrode7 is formed directly on the substrate 5, for example.

Example 7

In the present example, a liquid crystal cell for filling, having theliquid crystal layer having a thickness (d) of 4.5 m both in thereflection display section 9 and transmission display section 10 isproduced in the same manner as Example 1 except that the insulation film11 made of the insulation photosensitive resin is not formed on thesubstrate 5, and that, as shown in FIG. 4, the electrode pattern isformed in such a manner that the electrode 7 of the reflection displaysection 9 and the electrode 7 of the transmission display section 10 areelectrically isolated, so that a voltage is applied to each separatelyfrom outside the liquid crystal cell.

Then, the liquid crystal layer 1 is produced by filling the liquidcrystal composition having a difference of refractive index (n) of 0.065and positive dielectric constant anisotropy into the liquid crystal cellfor filling by means of vacuum injection.

Further, the phase difference compensation plates 16 and 17 andpolarization plates 14 and 15 are laminated to the outside of therespective electrode substrates of the above liquid crystal cell. Here,each of the phase difference compensation plates 16 and 17 is composedof two phase difference compensation plates. The lamination orientationof the phase difference compensation plates 16 and 17 and polarizationplates 14 and 15 is determined correspondingly to the alignmentdirection (alignment orientation) of the liquid crystal.

In the present example, the liquid crystal in the liquid crystal layer 1is aligned in parallel with the substrates 4 and 5 (parallel to thedisplay surface) with no twist, and the birefringence mode using theretardation of the liquid crystal layer 1 for the display is adopted asthe liquid crystal display method.

Also, in the present example, the retardation suitable for thereflection display is used for the transmission display section 10.Here, the reflection display section 9 is arranged in the same manner asits counterpart of Example 2 in Embodiment 2, while the transmissiondisplay section 10 is arranged differently from its counterpart ofExample 2 in that it has the liquid crystal layer as thick as the one inthe reflection display section 9. Thus, to assemble the liquid crystaldisplay of the present example, the liquid crystal display of Example 2is re-designed optically to determine the optical of the polarizationplates 14 and 15 and phase difference compensation plates 16 and 17. Inthe present example, the optical of the polarization plates 14 and 15and phase difference compensation plates 16 and 17 is determined in sucha manner that the transmission display section 10 can show satisfactorydark display.

In the present example, like in Example 2, parallel aligning alignmentfilms are used as the alignment films 2 and 3 to align the liquidcrystal in parallel with the display surface when no voltage is appliedto the liquid crystal layer 1, and the alignment treatment is applied tothese alignment films 2 and 3 in such a manner as to form the crossedrubbing angle of 180.

In the above alignment treatment, the angle of twist of the directorconfiguration of the liquid crystal (twist angle) is 0, and thealignment starts to change upon the voltage application from the centralportion of the liquid crystal in the layer thickness direction of theliquid crystal layer 1.

The optical of the polarization plates 14 and 15, phase differencecompensation plates 16 and 17, and the liquid crystal layer 1 (that is,the lamination orientation of the polarization plates 14 and 15, andphase difference compensation plates 16 and 17, and the alignmentorientation of the liquid crystal) in the liquid crystal display of thepresent example is set forth in Table 3 below for ready comparison withreference to a common orientation.

Comparative Example 3

In the present comparative example with respect to Example 7 above, acomparative liquid crystal display is assembled in the same manner asExample 7 except that the phase difference compensation plate 16 iscomposed of two phase difference compensation plates while the phasedifference compensation plate 17 is composed of a single phasedifference compensation plate, and that the optical of the polarizationplates 14 and 15 and phase difference compensation plates 16 and 17 isset in such a manner that the transmission display section 10 can showsatisfactory light display. The lamination orientation of the phasedifference compensation plates 16 and 17 and polarization plates 14 and15 is determined correspondingly to the alignment direction (alignmentorientation) of the liquid crystal.

In the present comparative example, like in Example 7, parallel aligningalignment films are used as the alignment films 2 and 3 to align theliquid crystal in parallel with the display surface when no voltage isapplied to the liquid crystal layer 1, and the alignment treatment isapplied to these alignment films 2 and 3 in such a manner as to form thecrossed rubbing angle of 180.

In the above alignment treatment, the angle of twist of the directorconfiguration of the liquid crystal (twist angle) is 0, and thealignment starts to change upon the voltage application from the centralportion of the liquid crystal in the layer thickness direction of theliquid crystal layer 1.

The optical of the polarization plates 14 and 15, phase differencecompensation plates 16 and 17, and the liquid crystal layer 1 (that is,the lamination orientation of the polarization plates 14 and 15, andphase difference compensation plates 16 and 17, and the alignmentorientation of the liquid crystal) in the comparative liquid crystaldisplay of the present comparative example is set forth in Table 3 belowfor ready comparison with reference to a common orientation.

Example 8

A liquid crystal display of the present example is assembled in the samemanner as Example 7 except that the thickness (d) of the liquid crystallayer in both the reflection display section 9 and transmission displaysection 10 is 7.5 m, and that the optical of the polarization plates 14and 15 and phase difference compensation plates 16 and 17 is set in sucha manner that reflection display section 9 can show satisfactoryreflection display by using the retardation suitable for thetransmission display.

To be more specific, in the present example, a liquid crystal cell forfilling, including the liquid crystal layer having a thickness (d) of7.5 m in both the reflection display section 9 and transmission displaysection 10, is produced in the same manner as Example 1 except that theinsulation film 11 made of the insulation photosensitive resin is notformed on the substrate 5, and that, as shown in FIG. 4, the electrodepattern is formed in such a manner that the electrode 7 of thereflection display section 9 and the electrode 7 of the transmissiondisplay section 10 are electrically isolated, so that a voltage isapplied to each separately from outside the liquid crystal cell.

Then, the liquid crystal layer 1 is produced by filling the liquidcrystal composition having a difference of refractive index (n) of 0.065and the positive dielectric constant anisotropy but the chiral dopantinto the above liquid crystal cell for filling by means of vacuuminjection.

Further, the phase difference compensation plates 16 and 17 andpolarization plates 14 and 15 are laminated to the outside of therespective electrode substrates of the above liquid crystal cell. Here,each of the phase difference compensation plates 16 and 17 is composedof two phase difference compensation plates. The lamination orientationof the phase difference compensation plates 16 and 17 and polarizationplates 14 and 15 is determined correspondingly to the alignmentdirection (alignment orientation) of the liquid crystal.

In the present example, the liquid crystal in the liquid crystal layer 1is aligned in parallel with the substrates 4 and 5 (parallel to thedisplay surface) with no twist, and the birefringence mode using theretardation of the liquid crystal layer 1 for the display is adopted asthe liquid crystal display method.

Also, in the present example, the retardation suitable for thetransmission display is used for the reflection display section 9. Here,the transmission display section 10 is arranged in the same manner asits counterpart of Example 2 in Embodiment 2, while the reflectiondisplay section 9 is arranged differently from its counterpart ofExample 2 in that it has the liquid crystal layer as thick as the one inthe transmission display section 10. Thus, to assemble the liquidcrystal display of the present example, the liquid crystal display ofExample 2 is re-designed optically to determine the optical of thepolarization plates 14 and 15 and phase difference compensation plates16 and 17. In the present example, the optical of the polarizationplates 14 and 15 and phase difference compensation plates 16 and 17 isdetermined in such a manner that satisfactory reflection display can beshown.

In the present example, like in Example 2, parallel aligning alignmentfilms are used as the alignment films 2 and 3 to align the liquidcrystal in parallel with the display surface when no voltage is appliedto the liquid crystal layer 1, and the alignment treatment is applied tothese alignment films 2 and 3 in such a manner as to form the crossedrubbing angle of 180.

In the above alignment treatment, the angle of twist of the directorconfiguration of the liquid crystal (twist angle) is 0, and thealignment starts to change upon the voltage application from the centralportion of the liquid crystal in the layer thickness direction of theliquid crystal layer 1.

The optical of the polarization plates 14 and 15, phase differencecompensation plates 16 and 17, and the liquid crystal layer 1 (that is,the lamination orientation of the polarization plates 14 and 15, andphase difference compensation plates 16 and 17, and the alignmentorientation of the liquid crystal) in the liquid crystal display of thepresent example is set forth in Table 3 below for ready comparison withreference to a common orientation.

The optical shown in Table 3 below is the position of each opticalelement on the display surface when the viewer observes the displaysurface, and when the phase difference compensation plate 16 or 17 iscomposed of more than one phase difference compensation plate, eachphase difference compensation plate forming the phase differencecompensation plate 16 or 17 is set forth in accordance with the actualposition from the viewer's side.

Since the liquid crystal layer 1 is aligned without any twist, thealignment orientation set forth in Table 3 below is the alignmentorientation (alignment orientation of the major axis of the liquidcrystal molecules) in the entire liquid crystal layer 1 when no voltageis applied, and it is identical with the orientation of the rubbingtreatment applied to the alignment film 2 on the substrate 4 side.

Each orientation is expressed in degrees from the reference directionset arbitrarily on the display surface, and the retardation of eachphase difference compensation plate is expressed in nm with respect to abeam of monochrome light having the wavelength of 550 nm.

TABLE 3 EXAMPLE 7 3* 8 PLATE 14 TRANSMISSION AXIS ORIENTATION (°) 0 0 0PLATE 16 PLATE SLOW AXIS ORIENTATION (°) 15 15 15 RETARDATION (nm) 270270 270 PLATE SLOW AXIS ORIENTATION (°) 165 165 165 RETARDATION (nm) 135135 135 LC LAYER 1 ALIGNMENT ORIENTATION (°) 75 75 75 PLATE PLATE SLOWAXIS ORIENTATION (°) 75 105 165 17 RETARDATION (nm) 135 270 70 PLATESLOW AXIS ORIENTATION (°) 135 — 135 RETARDATION (nm) 270 — 270 PLATE 15TRANSMISSION AXIS ORIENTATION (°) 60 0 60 3*: COMPARATIVE EXAMPLE 3PLATES 14 × 15: POLARIZATION PLATES PLATES 16 × 17: PHASE DIFFERENCECOMPENSATION PLATES

Comparative Example 4

A comparative liquid crystal display of the present comparative exampleis assembled in the same manner as Example 7 except that the liquidcrystal in the liquid crystal layer 1 is aligned in parallel with thesubstrates 4 and 5 (parallel to the display surface) and twisted by 70,and that the polarization converting function of the liquid crystallayer 1 effected by the twisted director configuration of the liquidcrystal layer 1 is used for the display.

To be more specific, in the present comparative example, a liquidcrystal cell for filling, including the liquid crystal layer having athickness (d) of 4.5 m in both the reflection display section 9 andtransmission display section 10, is produced in the same manner asExample 1 except that the insulation film 11 made of the insulationphotosensitive resin is not formed on the substrate 5, and that, asshown in FIG. 4, the electrode pattern is formed in such a manner thatthe electrode 7 of the reflection display section 9 and the electrode 7of the transmission display section 10 are electrically isolated, sothat a voltage is applied to each separately from outside the liquidcrystal cell. Further, the phase difference compensation plates 16 and17 and polarization plates 14 and 15 are laminated to the outside of therespective electrode substrates of the above liquid crystal cell. Here,each of the phase difference compensation plates 16 and 17 is composedof two phase difference compensation plates. The lamination orientationof the phase difference compensation plates 16 and 17 and polarizationplates 14 and 15 is determined correspondingly to the alignmentdirection (alignment direction) of the liquid crystal.

Further, in the present comparative example, parallel aligning alignmentfilms are used as the alignment films 2 and 3, so that the directorconfiguration of the liquid crystal is parallel to the display surfacewhen no voltage is applied, and the rubbing treatment is applied thesealignment films 2 and 3 in such a manner as to form the crossed rubbingangle of 250. The crossed rubbing angle is defined as above. Then, theliquid crystal layer 1 is produced by filling the liquid crystalcomposition having a difference of refractive index (n) of 0.065 andpositive dielectric constant anisotropy into a space between theelectrode substrates of the liquid crystal cell for filling by means ofvacuum injection. The above alignment treatment and the function of thechiral dopant added to the liquid crystal composition impart the angleof twist (twist angle) of 70 to the director configuration of the liquidcrystal. A concentration of the chiral dopant is adjusted to impart theabove specified twist angle. The liquid crystal layer 1 aligned in thismanner starts to change its alignment upon application of the voltagefrom the central portion thereof in its layer thickness direction.

Also, in the present comparative example, the product (n d) of adifference of the refractive index (n) of the liquid crystal compositionand a thickness (d) of the liquid crystal layer suitable for thereflection display is used for the transmission display section 10.Here, the reflection display section 9 is arranged in the same manner asits counterpart of Example 5 in Embodiment 2, while the transmissiondisplay section 10 is arranged differently from its counterpart ofExample 5 in Embodiment 2 in that it has the same liquid crystal layerthickness as the one in the reflection display section 9. Thus, toassemble the comparative liquid crystal display of the presentcomparative example, the liquid crystal display of Example 5 isre-designed optically to determine the optical of the polarizationplates 14 and 15 and phase difference compensation plates 16 and 17. Inthe present comparative example, the optical of the polarization plates14 and 15 and phase difference compensation plates 16 and 17 isdetermined in such a manner that the transmission display section 10 canshow satisfactory dark display.

The optical of the polarization plates 14 and 15, phase differencecompensation plates 16 and 17, and the liquid crystal layer 1 (that is,the lamination orientation of the polarization plates 14 and 15, andphase difference compensation plates 16 and 17, and the alignmentorientation of the liquid crystal) in the comparative liquid crystaldisplay of the present comparative example is set forth in Table 4 belowfor ready comparison with a reference to a common orientation.

Comparative Example 5

In the present comparative example, a comparative liquid crystal displayis assembled in the same manner as Comparative Example 4 except that thepolarization plates 14 and 15 and phase difference compensation plates16 and 17 are optically positioned in such a manner that thetransmission display section 10 can show satisfactory light display. Tobe more specific, a comparative liquid crystal display is assembled inthe same manner as Example 7 except that: (1) the polarization plates 14and 15 and phase difference compensation plates 16 and 17 are opticallypositioned in such a manner that the transmission display section 10 canshow satisfactory light display, (2) the liquid crystal in the liquidcrystal layer 1 is aligned in parallel with the substrates 4 and 5(parallel to the display surface) and twisted by 70, and (3) thepolarization converting function of the liquid crystal layer 1 effectedby the twisted alignment thereof is used for the display.

The optical of the polarization plates 14 and 15, phase differencecompensation plates 16 and 17, and the liquid crystal layer 1 (that is,the lamination orientation of the polarization plates 14 and 15, andphase difference compensation plates 16 and 17, and the alignmentorientation of the liquid crystal) in the comparative liquid crystaldisplay of the present comparative example is set forth in Table 4 belowfor ready comparison with reference to a common orientation.

Example 9

In the present example, a liquid crystal display is assembled in thesame manner as Example 8 except that (1) the phase differencecompensation plate 16 is composed of two phase difference compensationplates while the phase difference compensation plate 17 is composed of asingle phase difference compensation plate, (2) the liquid crystal inthe liquid crystal layer 1 is aligned in parallel with the substrates 4and 5 (parallel to the display surface) and twisted by 70, and (3) thepolarization converting function of the liquid crystal layer 1 effectedby the twisted alignment thereof is used for the display.

To be more specific, in the present example, a liquid crystal cell forfilling, including the liquid crystal layer having a thickness (d) of7.5 m both in the reflection display section 9 and transmission displaysection 10, is produced in the same manner as Example 1 except that theinsulation film 11 made of the insulation photosensitive resin is notformed on the substrate 5, and that, as shown in FIG. 4, the electrodepattern is formed in such a manner that the electrode 7 of thereflection display section 9 and the electrode 7 of the transmissiondisplay section 10 are electrically isolated, so that a voltage isapplied to each separately from outside the liquid crystal cell.

Further, the phase difference compensation plates 16 and 17 andpolarization plates 14 and 15 are laminated to the outside of therespective electrode substrates of the above liquid crystal cell. Here,the phase difference compensation plate 17 is composed of a single phasedifference compensation plate, while the phase difference compensationplate 16 is composed of two phase difference compensation plates. Thelamination orientation of the phase difference compensation plates 16and 17 and polarization plates 14 and 15 is determined correspondinglyto the alignment direction (alignment orientation) of the liquidcrystal.

In the present example, the liquid crystal display is assembled in sucha manner that the twist director configuration of the liquid crystallayer 1 (angle of twist of the director configuration of the liquidcrystal (twist angle)) is 70. More specifically, parallel aligningalignment films are used as the alignment films 2 and 3, so that thedirector configuration of the liquid crystal is parallel to the displaysurface when no voltage is applied, and the alignment treatment isapplied to these alignment films 2 and 3 by means of rubbing in such amanner as to form the crossed rubbing angle of 250. The crossed rubbingangle is defined as above. Then, the liquid crystal layer 1 is producedby filling the liquid crystal composition having a difference ofrefractive index (n) of 0.065 and positive dielectric constantanisotropy into a space between the electrode substrates of the liquidcrystal cell for filling by means of vacuum injection. The abovealignment treatment and the function of the chiral dopant added to theliquid crystal composition impart the angle of twist (twist angle) of 70to the director configuration of the liquid crystal. A concentration ofthe chiral dopant is adjusted in such a manner as to impart the abovespecified twist angle to the director configuration of the liquidcrystal. The liquid crystal layer 1 aligned in this manner starts tochange its alignment upon the voltage application from the centralportion thereof in its layer thickness direction.

In the present example, the product (n d) of a difference of therefractive index (n) of the liquid crystal composition and a thickness(d) of the liquid crystal layer suitable for the transmission display isused for the reflection display section 9. Here, the transmissiondisplay section 10 is arranged in the same manner as its counterpart ofExample 5 in Embodiment 2, while the reflection display section 9 isarranged differently from its counterpart of Example 5 in that it hasthe same liquid crystal layer thickness as the one in the transmissiondisplay section 10. Thus, to assemble the liquid crystal display of thepresent example, the liquid crystal display of Example 5 is re-designedoptically to determine the optical of the polarization plates 14 and 15and phase difference compensation plates 16 and 17. In the presentexample, the optical of the polarization plates 14 and 15 and phasedifference compensation plates 16 and 17 is determined in such a mannerthat satisfactory reflection display can be shown.

The optical of the polarization plates 14 and 15, phase differencecompensation plates 16 and 17, and the liquid crystal layer 1 (that is,the lamination orientation of the polarization plates 14 and 15, andphase difference compensation plates 16 and 17, and the alignmentorientation of the liquid crystal) in the liquid crystal display of thepresent example is set forth in Table 4 below for ready comparison withreference to a common orientation.

The optical shown in Table 4 is the position of each optical element onthe display surface when the viewer observes the display surface, andwhen the phase difference compensation plate 16 or 17 is composed ofmore than one phase difference compensation plate, each phase differencecompensation plate forming the phase difference compensation plate 16 or17 is set forth in accordance with the actual position from the viewer'sside. Also, in Table 4, each orientation is expressed in degrees fromthe reference orientation set arbitrarily on the display surface, andthe retardation of each phase difference compensation plate is expressedin nm with respect to a beam of monochrome light having the wavelengthof 550 nm.

TABLE 4 EXAMPLE 4* 5* 9 PLATE 14 TRANSMISSION AXIS ORIENTATION (°) 0 0 0PLATE 16 PLATE SLOW AXIS ORIENTATION (°) 18 18 18 RETARDATION (nm) 270270 127 PLATE SLOW AXIS ORIENTATION (°) 126 126 126 RETARDATION (nm) 135135 135 LC LAYER 1 SUBSTRATE 4 ALIGNMENT 16 16 16 ORIENTATION (°)SUBSTRATE 5 ALIGNMENT 86 86 86 ORIENTATION (°) PLATE PLATE SLOW AXISORIENTATION (°) 36 36 −4 17 RETARDATION (nm) 135 135 260 PLATE SLOW AXISORIENTATION (°) 96 108 — RETARDATION (nm) 270 270 — PLATE 15TRANSMISSION AXIS ORIENTATION (°) 21 0 152 4*: COMPARATIVE EXAMPLE 4 5*:COMPARATIVE EXAMPLE 5 PLATES 14 × 15: POLARIZATION PLATES PLATES 16 ×17: PHASE DIFFERENCE COMPENSATION PLATES

As has been explained, in the liquid crystal display of Example 7 andthe comparative liquid crystal displays of Comparative Examples 3through 5, a thickness (d) of the liquid crystal layer is set to 4.5 m,so that satisfactory reflection display can be shown. Thus, in Example 7and Comparative Examples 3 through 5, the optical of the polarizationplate 14 and phase difference compensation plate 16, which areresponsible for the reflection display alone, is set to be suitable forthe reflection display. On the other hand, the thickness of the liquidcrystal layer of the transmission display section 10 is set differentlyfrom the one in its counterpart of each Example in Embodiment 2. Thus,in Example 7 and Comparative Examples 3 through 5, the optical of thephase difference compensation plate 17 and polarization plate 15 is setindividually in accordance with the optical characteristics of thetransmission display section 10. In other words, in Example 7 andComparative Example 4, the liquid crystal displays which can realize thesatisfactory dark display are assembled, and in Comparative Examples 3and 5, the liquid crystal displays which can realize satisfactory lightdisplay are assembled.

In contrast, in the liquid crystal displays of Examples 8 and 9, athickness (d) of the liquid crystal layer is set to 7.5 m, so thatsatisfactory transmission display can be shown. For this reason, inExamples 8 and 9, the optical of the polarization plate 14, phasedifference control plates 16 and 17, and polarization plate 15 is set tobe suitable for the transmission display. Thus, in Examples 8 and 9, thedisplay characteristics of the reflection display section 9 aredetermined by the optical of the polarization plate 14 and phasedifference compensation plate 16 whose optical is set for thetransmission display.

In addition, the display characteristics of the liquid crystal displaysassembled in Example 7, Comparative Example 3, Example 8, ComparativeExamples 4 and 5, and Example 9 are graphed in FIGS. 11 through 15,respectively. These display characteristics were measured through themicroscope in the same manner as Example 1, and in each drawing, thehorizontal axis represents a root mean square value of the appliedvoltage, and the vertical axis represents the brightness (reflectance ortransmittance). Here, the transmittance of the transmitting displaysection 10 when the polarization plates 14 and 15 are not provided isscaled as 100%, and the reflectance of the reflection display section 9before the polarization plate 14 is provided is scaled as 100%.

In FIG. 11, a curve 261 represents the voltage dependence of thereflectance of the reflection display section 9 versus a voltage acrossthe electrodes 6 and 7, and a curve 262 represents the voltagedependence of the transmittance of the transmission display section 10versus a voltage across the electrodes 6 and 7 in the liquid crystaldisplay assembled in Example 7.

FIG. 11 reveals that, in Example 7, while the applied voltage is in arange between 1V and 3V, the transmittance increases with an increasingapplied voltage. On the other hand, the reflectance increases with anincreasing applied voltage while the applied voltage is in a rangebetween 1V and 2V, and decreases with an increasing applied voltageafter the applied voltage exceeds 2V. That is, when the applied voltageis 1V, the reflectance of the reflection display section 9 and thetransmittance of the transmission display section 10 are both 3%. Whenthe applied voltage is increased to 2V, both increase to 40% and 18%,respectively, and when the applied voltage is increased further to 3V,the reflectance of the reflection display section 9 decreases to 28%,while the transmittance of the transmission display section increasesfurther to 33%.

In FIG. 12, a curve 271 represents the voltage dependence of thereflectance of the reflection display section 9 versus a voltage acrossthe electrodes 6 and 7, and a curve 272 represents the voltagedependence of the transmittance of the transmission display section 10versus a voltage across the electrodes 6 and 7 in the liquid crystaldisplay assembled in Comparative Example 3.

FIG. 12 reveals that, in Comparative Example 3, while the appliedvoltage is in a range between 1V and 2V, both the reflectance andtransmittance increase with an increasing applied voltage. That is, whenthe applied voltage is 1V, the reflectance of the reflection displaysection 9 and the transmittance of the transmission display section 10are 3% and 18%, respectively, and when the applied voltage is increasedto 2V, both increase to 40%.

In FIG. 13, a curve 281 represents the voltage dependence of thereflectance of the reflection display section 9 versus a voltage acrossthe electrodes 6 and 7, and a curve 282 represents the voltagedependence of the transmittance of the transmission display section 10versus a voltage across the electrodes 6 and 7 in the liquid crystaldisplay assembled in Example 8.

FIG. 13 reveals that, in Example 8, while the applied voltage is in arange between 1V and 2V, the transmittance increases with an increasingapplied voltage. On the other hand, the reflectance increases with anincreasing applied voltage when the applied voltage is in a rangebetween 0.7V and 1.2V, decreases with an increasing applied voltage whenthe applied voltage is in a range between 1.2V and 1.7V, and increasesagain with an increasing applied voltage when the applied voltage is ina range between 1.7V and 2.3V. That is, when the applied voltage is 1V,the reflectance of the reflection display section 9 and thetransmittance of the transmission display section 10 are 24% and 3%,respectively. When the applied voltage is increased to 1.2V, thereflectance of the reflection display section 9 increases to 40%. Whenthe applied voltage is further increased to 1.7V, the reflectance of thereflection display section 9 decreases to 3%. When the applied voltageis further increased to 2V, both the reflectance of the reflectiondisplay section 9 and the transmittance of the transmission displaysection 10 increase to 27% and 39%, respectively.

In FIG. 14, a curve 291 represents the voltage dependence of thereflectance of the reflection display section 9 versus a voltage acrossthe electrodes 6 and 7, and a curve 292 represents the voltagedependence of the transmittance of the transmission display section 10versus a voltage across the electrodes 6 and 7 in the liquid crystaldisplay assembled in Comparative Example 4.

FIG. 14 reveals that, in Comparative Example 4, while the appliedvoltage is in a range between 1.2V and 3V, both the reflectance andtransmittance increase with an increasing applied voltage. That is, whenthe applied voltage is 1.2V, the reflectance of the reflection displaysection 9 and the transmittance of the transmission display section 10are 3% and 1%, respectively, and when the applied voltage is increasedto 3V, both increase to 36% and 16%, respectively.

In FIG. 15, a curve 311 represents the voltage dependence of thereflectance of the reflection display section 9 versus a voltage acrossthe electrodes 6 and 7, and a curve 312 represents the voltagedependence of the transmittance of the transmission display section 10versus a voltage across the electrodes 6 and 7 in the liquid crystaldisplay assembled in Comparative Example 5.

FIG. 15 reveals that, in Comparative Example 5, while the appliedvoltage is in a range between 1.2V and 3V, both the reflectance andtransmittance increase with an increasing applied voltage. That is, whenthe applied voltage is 1.2V, the reflectance of the reflection displaysection 9 and the transmittance of the transmission display section 10are 3% and 21%, respectively, and when the applied voltage is increasedto 3V, both increase to 39% and 35%, respectively.

In FIG. 16, a curve 321 represents the voltage dependence of thereflectance of the reflection display section 9 versus a voltage acrossthe electrodes 6 and 7, and a curve 322 represents the voltagedependence of the transmittance of the transmission display section 10versus a voltage across the electrodes 6 and 7 in the liquid crystaldisplay assembled in Example 9.

FIG. 16 reveals that, in Example 9, while the applied voltage is in arange between 1.2V and 3V, the transmittance increases with anincreasing applied voltage. On the other hand, when the applied voltageis in a range between 0.9 and 1.7V, the reflectance decreases with anincreasing applied voltage, and then increases with an increasingapplied voltage. That is, when the applied voltage is 1.2V, thereflectance of the reflection display section 9 and the transmittance ofthe transmission display section 10 are 7% and 32%, respectively, andwhen the applied voltage is increased to 1.7V, the reflectance of thereflection display section 9 decreases to 3%, and when the appliedvoltage is further increased to 3V, both the reflectance of thereflection display section 9 and the transmittance of the transmissiondisplay section 10 increase to 37% and 36%, respectively.

The above Examples and Comparative Examples discussed a liquid crystaldisplay exploiting the change in the polarization state caused by thepolarization converting function of the liquid crystal layer 1, such asretardation and optical rotatory polarization, provided with thepolarization plates 14 and 15, and having equal thicknesses of theliquid crystal layer 1 in the reflection display section 9 andtransmission display section 10. In this case, when the same voltage isapplied to the respective electrodes 7 of the reflection display section9 and transmission display 10 (when the reflection display section 9 andtransmission display section 10 are driven by the same voltage), if, asin Example 7 and Comparative Examples 3 through 5, a voltage which canattain satisfactory brightness and contrast ratio for the light displayin the reflection display section 9 is applied, the brightness andcontrast ratio for the light display in the transmission display section10 are not satisfactory, and if, as in Example 7 and ComparativeExamples 3 through 5, a voltage which can attain satisfactory brightnessand contrast ratio for the light display in the transmission displaysection 10 is applied, the brightness in the reflection display section9 and the brightness in the transmission display section 10 do notchange in the same manner, thereby making satisfactory displayimpossible.

However, the liquid crystal displays of Examples 7 through 9 can solvethe above problem and show satisfactory display by applying differentvoltages to the respective electrodes 7 in the reflection displaysection 9 and transmission display section 10 (by driving the reflectiondisplay section 9 and transmission display section 10 using differentrespective voltages).

In other words, any of the liquid crystal displays of Examples 7 through9 can attain satisfactory brightness and contrast ratio for the lightdisplay both in the reflection display section 9 and transmissiondisplay section 10 by applying different respective voltages to theelectrode 7 of the transmission display section 10 and the electrode 7of the reflection display section 9. At the same time, the reflectiondisplay section 9 and transmission display section 10 can show the samedisplay state, that is, either the light or dark display, therebyrealizing the display with excellent visibility.

It is understood from the comparison of the present embodiment andEmbodiment 2 that it is effective to make the liquid crystal layer 1thicker in the transmission display section 10 than in the reflectiondisplay section 9 to attain the satisfactory brightness and contrastratio for the light display both in the reflection display section 9 andtransmission display section 10 of the liquid crystal display using thepolarization converting function, such as the retardation and opticalrotatory polarization of the liquid crystal layer 1, with the use of thepolarization plates 14 and 15.

In the liquid crystal display mode adopted in each example of thepresent embodiment and Embodiment 2, the director configuration of theliquid crystal when no voltage is applied is parallel to the planesurface direction of the display surface. It should be appreciated that,however, other modes, such as vertical alignment mode and hybridalignment mode, are also applicable by using the liquid crystalmaterials of different kinds from those disclosed in the above examplesor using the alignment film having different properties from those ofthe alignment film disclosed above.

Further, it should be appreciated that satisfactory opticalcharacteristics can be attained by the present invention using anyliquid crystal display mode which exploits the retardation or opticalrotatory polarization of the liquid crystal layer 1, provided that, inthe display mode used, the thickness of the liquid crystal layer affectsthe optical characteristics, and that a liquid crystal layer thicknesswhich is thinner in the reflection display section 9 than in thetransmission display section 10 is suitable for the display mode used.

Furthermore, it is understood that the liquid crystal displays ofExamples 4 and 7 through 9 can show the satisfactory display whensupplied with different voltages to the reflection display section 9 andtransmission display section 10 by means of the electrodes 6 and 7(alignment mechanism). In this case, the liquid crystal displays ofExamples 4 and 7 can show satisfactory display when a sufficiently highvoltage is applied to the transmission display section 10. Also, theliquid crystal displays of Examples 8 and 9 can show satisfactorydisplay by adjusting the voltage at the reflection display section 9.Thus, according to the present embodiment and Embodiment 2, satisfactorydisplay can be shown by producing the liquid crystal cell beforehand insuch a manner that different voltages can be applied to the reflectiondisplay section 9 and transmission display section 10, besides bychanging the thickness of the liquid crystal layer in the reflectiondisplay section 9 and transmission display section 10.

Embodiment 4

Explained in the present embodiment is a liquid crystal display whichcan realize satisfactory reflection display and transmission display byproviding different director configurations of the liquid crystal in thereflection display section and transmission display section by changingthe alignment treatment orientation (rubbing orientation) on thesubstrate, which is a factor that determines the director configurationof the liquid crystal, that is, the alignment treatment orientation ofthe alignment film provided to each electrode substrate in thereflection display section and transmission display section.

In the present embodiment, a so-called rubbing method is adopted toalign the liquid crystal layer uniformly. In the present embodiment, atleast two different director configurations of the liquid crystal can berealized by covering the surface of the alignment film with thephotoresist or the like before subjecting the alignment film to therubbing treatment, so that the alignment film provided to each electrodesubstrate can be given different respective alignment treatmentorientations in the reflection display section and transmission displaysection. According to the above method, the director configuration ofthe liquid crystal suitable for the reflection display and the directorconfiguration of the liquid crystal suitable for the transmissiondisplay can be realized at the same time, thereby realizing satisfactoryreflection display and transmission display.

In the following, the liquid crystal display of the present embodimentwill be explained in detail, and hereinafter, like components arelabeled with like reference numerals with respect to Embodiments 1through 3, and, for ease of explanation, the description of thesecomponents is not repeated here.

In the first place, the process of alignment treatment of the substrate(electrode substrate 40) used in the liquid crystal display of thepresent embodiment will be explained with reference to FIGS. 17 and 18(a) through 18(e).

As shown in FIG. 18( a), an alignment film material is applied over asubstrate 41 (equivalent to the substrate 4 on which is formed theelectrode 6 or the substrate 5 on which are formed the electrodes 7) ofthe liquid crystal cell on the surface thereof touching the liquidcrystal layer 1 (S1). Then, the alignment film material is pre-baked(S2) and cured (S3), whereby an alignment film 42 (equivalent to thealignment film 2 or 3) is formed over the substrate 41 on the surfacethereof touching the liquid crystal layer 1.

Then, the alignment film 42 is subjected to the rubbing treatment, andas a consequence, the alignment treatment is applied to the electrodesubstrate 40 which includes the alignment film 42 at the interface withthe liquid crystal layer 1 of the substrate 41. Here, in the presentembodiment, as shown in FIG. 18( b), screening is carried out by ascreen resist 43 for the rubbing treatment, so that the rubbingtreatment is applied partially. In this case, a resist material for thescreen for the rubbing treatment is applied over the alignment film 42(S4). Then, the resist material is pre-baked (S5), exposed to UV rayswith masking to expose portions (first alignment treatment regions 42 a)of the alignment film 42 (S6), developed (S7), and cured (S8), afterwhich the rubbing treatment is applied to the first alignment treatmentregions 42 a (S9). Then, after the rubbing treated electrode substrate40 is cleaned (S10), the resist 43 is removed as shown in FIG. 18( c)(S11).

Subsequently, to realize an director configuration of the liquid crystaldifferent from the director configuration of the liquid crystal on thefirst alignment treatment regions 42 a, as shown in FIG. 18( d), rubbedportions (first alignment treatment regions 42 a) are protected by ascreen resist 44 for the rubbing treatment, and the rubbing treatment isapplied to portions which have not been rubbed. To be more specific, aresist material of the screen for the rubbing treatment is applied overthe alignment film 42 from which the resist 43 was removed (S12). Then,the resist material is pre-baked (S13), exposed to UV rays with maskingin such a manner that portions (second alignment treatment regions 42 b)other than the first alignment treatment regions 42 a on the alignmentfilm 42 are exposed (S14), developed (S15), and cured (S16).Subsequently, the second alignment treatment regions 42 b are subjectedto the rubbing treatment in such a manner that the treatmentorientations are different in the first and second alignment treatmentregions 42 a and 42 b (S17). Then, after the rubbing treated electrodesubstrate 40 is cleaned (S18), the resist 44 is removed as shown in FIG.18( e) (S19). Consequently, the alignment film 42 (alignment mechanism),to which the alignment treatment has been applied twice in differentorientations, is obtained.

As has been explained, in the present embodiment, the alignmenttreatment is applied at least twice with the patterning by means of theresist. Here, at least two different director configurations of theliquid crystal (for example, various kinds of planer alignments havingtheir respective aligning directions) can be obtained by changing thetreatment orientation for each alignment treatment (in the aboveexplanation, the alignment treatment is effected in two differentorientations by applying the alignment treatment twice). If thealignment treatment orientation is changed on at least one of thesubstrates (electrode substrates) in the above manner, the alignmentsare provided to the reflection display section 9 and transmissiondisplay section 10 independently, thereby making it possible to realizesatisfactory display.

Next, a liquid crystal display having different director configurationsof the liquid crystal in the reflection display section 9 andtransmission display section 10 and using the polarization plates 14 and15 will be explained by way of examples for purposes of explanationonly, without any intention as a definition of the limits of theinvention.

Example 10

In the present example, a liquid crystal display is assembled in thesame manner as Comparative Example 5. To be more specific, a liquidcrystal cell for filling, including the liquid crystal layer having athickness (d) (cell gap) of 4.5 m both in the reflection display section9 and transmission display section 10, is produced in the same manner asExample 1 except that the insulation film 11 made of the insulationphotosensitive resin is not formed on the substrate 5, and that, asshown in FIG. 4, the electrode pattern is formed in such a manner thatthe electrode 7 of the reflection display section 9 and the electrode 7of the transmission display section 10 are electrically isolated, sothat a voltage is applied to each separately from outside the liquidcrystal cell. Then, the phase difference compensation plates 16 and 17and polarization plates 14 and 15 are laminated to the outside of therespective electrode substrates of the above liquid crystal cell. Here,each of the phase difference compensation plates 16 and 17 is composedof two phase difference compensation plates.

In the present example, the alignment film 3 is subjected to the rubbingtreatment in different orientations in the same manner as shown in FIGS.17 and 18( a) through 18(e). To be more specific, in the presentexample, the alignment film 2 on the substrate 4 side is rubbed in thesame orientation both in the reflection display section 9 andtransmission display section 10, whereas the alignment film 3 (alignmentmechanism) on the substrate 5 side is rubbed in such a manner thealignment orientations of the liquid crystal are different in thereflection display section 9 and transmission display section 10.

In the present example, the reflection display section 9 adopts a liquidcrystal display mode, in which the liquid crystal is aligned in parallelwith the display surface (parallel to the substrates 4 and 5) with atwist, and the transmission display section 10 adopts a liquid crystaldisplay mode, in which the liquid crystal is aligned in parallel withthe display surface (parallel to the substrates 4 and 5) without twist.

Also, in the present example, the liquid crystal display is assembled insuch a manner that, in the reflection display section 9, n d of theliquid crystal layer 1 is approximately 270 nm and the angle of twist ofthe director configuration of the liquid crystal (twist angle) is 70,and in the transmission display section 10, n d of the liquid crystallayer 1 is approximately 270 nm and the angle of twist of the liquidcrystal (twist angle) is 0. Thus, the liquid crystal display assembledin the above manner can show satisfactory display both in the reflectiondisplay section 9 and transmission display section 10 while having theliquid crystal layer 1 provided continuously across the reflectiondisplay section 9 and transmission display section 10 without changingthe cell gap.

The optical of the polarization plates 14 and 15, phase differencecompensation plates 16 and 17, and the liquid crystal layer 1 (that is,the lamination orientation of the polarization plates 14 and 15, andphase difference compensation plates 16 and 17, and the alignmentorientation of the liquid crystal) in the reflection display section 9and transmission display section 10 in the liquid crystal display of thepresent example is set forth in Table 5 below for ready comparison withreference to a common orientation.

The optical shown in Table 5 is the position of each optical element onthe display surface when the viewer observes the display surface, andwhen the phase difference compensation plate 16 or 17 is composed ofmore than one phase difference compensation plate, each phase differencecompensation plate forming the phase difference compensation plate 16 or17 is set forth in accordance with the actual position from the viewer'sside. Also, in Table 5, each orientation is expressed in degrees fromthe reference orientation set arbitrarily on the display surface, andthe retardation of each phase difference compensation plate is expressedin nm with respect to a beam of monochrome light having the wavelengthof 550 nm.

TABLE 5 EXAMPLE 10 SEC. 9 SEC. 10 PLATE 14 TRANSMISSION AXIS 0ORIENTATION (°) PLATE PLATE SLOW AXIS ORIENTATION (°) 15 16 RETARDATION(nm) 270 PLATE SLOW AXIS ORIENTATION (°) 75 RETARDATION (nm) 135 LCLAYER 1 SUBSTRATE 4 −15 −15 ALIGNMENT ORIENTATION (°) SUBSTRATE 5 55 −15ALIGNMENT ORIENTATION (°) PLATE PLATE SLOW AXIS ORIENTATION (°) −15 17RETARDATION (nm) 115 PLATE SLOW AXIS ORIENTATION (°) −75 RETARDATION(nm) 270 PLATE 15 TRANSMISSION AXIS 90 ORIENTATION (°) SEC. 9: SECTION 9SEC. 10: SECTION 10 PLATES 14 × 15: POLARIZATION PLATES PLATES 16 × 17:PHASE DIFFERENCE COMPENSATION PLATES

Next, the operation of each optical element in the present embodimentwill be explained in the following.

First, a case where no voltage is applied to the liquid crystal layer 1will be explained. In this case, the liquid crystal in the liquidcrystal layer 1 is aligned along the alignment of the interface of thesubstrate touching the liquid crystal layer 1, that is, the alignmenttreatment orientation of the alignment films 2 and 3 provided on theirrespective electrode substrates. For example, when the chiral dopant isnot added to the liquid crystal composition in the liquid crystaldisplay of Example 10, the liquid crystal is twisted 70 to the left inthe reflection display section 9, and 0, that is, not twisted, in thetransmission display section 10.

For this reason, if no voltage is applied to the liquid crystal layer 1,given 270 nm as n d of the liquid crystal layer 1, circularly polarizedlight entering the liquid crystal layer 1 is converted to linearlypolarized light before it exits from the reflection display section 9.Thus, light entering the liquid crystal layer 1 from the polarizationplate 14 side is converted to circularly polarized light by the phasedifferent compensation plate 16, then converted to linearly polarizedlight by the liquid crystal layer 1, which exits from the liquid crystallayer 1 and reaches the reflection film 8. If the linearly polarizedlight is reflected by the reflection film 8, the reflected light isconverted again into the transmission components of the polarizationplate 14. Consequently, in the above liquid crystal display, thereflection display section 9 shows light display when no voltage isapplied to the liquid crystal layer 1.

On the other hand, if no voltage is applied to the liquid layer 1, given250 nm-270 nm as n d of the liquid crystal layer 1, the liquid crystallayer 1 functions as the ½ wavelength plate in the transmission displaysection 10. To be more specific, circularly polarized light entering theliquid crystal layer 1 is converted to another circularly polarizedlight that is orthogonal to the incident circularly polarized light atright angles. For example, if the incident circularly polarized light isright, then it is converted to left circularly polarized light, and ifthe incident circularly polarized is left, then it is converted to rightcircularly polarized light. In the transmission display section 10, theincident light passes through the polarization plate 15, and enters theliquid crystal layer 1 after it is converted to circularly polarizedlight by the phase difference compensation plate 17. In Example 10,substantially left circularly polarized light enters the liquid crystallayer 1 from the phase difference compensation plate 17, and isconverted to right circularly polarized light. Here, right circularlypolarized light is converted to linearly polarized light along thetransmission axis direction of the polarization plate 14 by the phasedifference compensation plate 16, while left circularly polarized lightis converted to linearly polarized light along the absorption axisdirection of the polarization plate 14. Thus, the transmission displaysection 10 of the above liquid crystal display shows light display whenno voltage is applied to the liquid crystal layer 1.

Next, a case where a voltage is applied to the liquid crystal layer 1will be explained. While a voltage is applied to the liquid crystallayer 1, the liquid crystal in the liquid crystal layer 1 is alignedperpendicular to the substrates 4 and 5 in response to the appliedvoltage in both the reflection display section 9 and transmissiondisplay section 10, whereby the above polarization converting functionbecomes less effective. In other words, the incident circularlypolarized light from the phase difference compensation plates 16 and 17passes through the liquid crystal layer 1 directly. Consequently, boththe reflection display section 9 and transmission display section 10show the dark display.

In Example 10, the phase difference compensation plate 17 is composed ofa phase difference compensation plate having the retardation of 115 nm.It is preferable that the phase difference compensation plate 17 has theretardation of about 135 nm to realize satisfactory circularly polarizedlight by the phase difference compensation plate 17 alone. However, theretardation of the liquid crystal layer 1 in the transmission displaysection 10 is not lost completely at a practical voltage level, and inconsideration of this fact, the retardation of the phase differencecompensation plate 17 is set in such a manner as to obtain satisfactorycontrast.

The phase difference compensation plate 16 is furnished with a functionof converting light entering the liquid crystal layer 1 in thereflection display section 9 into circularly polarized light with awavelength in a broad range. In the above liquid crystal display, theliquid crystal layer 1 in the reflection display section 9 is twisted70, and n d thereof is set to 270 nm. Thus, circularly polarized lightenters the liquid crystal layer 1 in the reflection display section 9,and is converted to linearly polarized light by the liquid crystal layer1 while it passes through the same and reaches the reflection film 8.Then, the linearly polarized light having reached the reflection film 8is reflected on the mirror surface thereof, and passes through eachoptical element in the reversed order. Consequently, the reflected lightis converted to linearly polarized light having an oscillating electricfield along the transmission axis orientation of the polarization plate14. Hence, the reflection display section 9 shows the light display.

Here, the liquid crystal composition used herein is blended with thechiral dopant for imparting a natural twist to the left to the directorconfiguration of the liquid crystal. The chiral dopant changes thenatural helical pitch of the liquid crystal composition depending on itsconcentration in the liquid crystal composition. Thus, by exploiting thefact that the lowest voltage at which the director configuration of theliquid crystal starts to change varies with the helical pitch, thevoltage dependencies of the brightness in the reflection display section9 and transmission display section 10 can be matched if the helicalpitch is adjusted adequately.

The display characteristics of the liquid crystal display of Example 10assembled in the above manner are graphed in FIG. 19. The displaycharacteristics of FIG. 19 were measured in the same manner as Example1, and in the drawing, the horizontal axis represents a root mean squarevalue of the applied voltage and the vertical axis represents thebrightness (reflectance or transmittance).

In FIG. 19, a curve 331 indicates the voltage dependence of thereflectance of the reflection display section 9, and a curve 332indicates the voltage dependence of the transmittance of thetransmission display section 10 in the liquid crystal display of Example10.

As can be understood from FIG. 19, the liquid crystal display of Example10 shows the light display when no voltage is applied, and it canrealize the display in the so-called normally white (NW) mode, in whichboth the reflectance and transmittance decrease with an increasingapplied voltage. In the present liquid crystal display, not only can thecontrast ratio be set to substantially the same value in the reflectiondisplay section 9 and transmission display section 10, but also thereflection display section 9 and transmission display section 10 canshow either the dark or light display simultaneously, thereby realizingthe display with excellent visibility.

As has been explained, setting different twist angles of the liquidcrystal layer 1 in the reflection display section 9 and transmissiondisplay section 10 as the means for changing the director configurationof the liquid crystal in the reflection display section 9 andtransmission display section 10 is effective to realize satisfactorydisplay both in the reflection display section 9 and transmissiondisplay section 10.

In Example 10, to change the twist angle of the liquid crystal layer 1in the reflecting display section 9 and transmission display section 10,the rubbing treatment is applied in different orientations in thereflecting display section 9 and transmission display section 10, sothat the director configuration of the liquid crystal layer 1 is twistedin the reflection display section 9 but not in the transmission displaysection 10. However, means for changing the twist angle of the liquidcrystal layer 1 in the reflection display section 9 and transmissiondisplay section 10 is not especially limited.

For example, besides the above combination, the following combinationsare applicable: (1) the director configuration of the liquid crystallayer 1 is twisted in both the reflecting display section 9 andtransmission display section 10, but the twist angles or theorientations of the twist are different; (2) the director configurationof the liquid crystal layer 1 is twisted in the transmission displaysection 10 but not in the reflection display section 9; (3) the tilts(so-called pre-tilts) of the liquid crystal with respect to thesubstrates 4 and 5 are different in the reflection display section 9 andtransmission display section 10; (4) the change of the directorconfiguration of the liquid crystal at the substrate interface iscombined with other means of the present invention; (5) different cellgaps are provided to the reflection display section 9 and transmissiondisplay section 10; and (6) different electric fields are generated inthe reflection display section 9 and transmission display section 10.

Embodiment 5

In each example of Embodiments 2 through 4, the arrangement forrealizing satisfactory reflection display and transmission display onthe liquid crystal display using the liquid crystal aligned in parallelwith the substrates was explained. In the present embodiment, a liquidcrystal display whose alignment orientation of the liquid crystal isperpendicular to the substrates, like the one in Example 1 of Embodiment1, will be explained. Note that, however, the dichroic dye is notblended in the liquid crystal layer, and the liquid crystal display isdesigned in such a manner as to show the display using the polarizationplate while exploiting the birefringence or optical rotatorypolarization (polarization converting function) of the liquid crystal.Hereinafter, like components are labeled with like reference numeralswith respect to Embodiments 1 through 4, and, for ease of explanation,the description of these components is not repeated here.

In the liquid crystal display of the present embodiment, liquid crystalhaving negative dielectric constant anisotropy is used in the liquidcrystal layer 1. Also, vertical aligning alignment films are used forthe alignment films 2 and 3 for sandwiching the liquid crystal layer 1.In this case, the liquid crystal molecules are aligned substantiallyperpendicular to the substrates 4 and 5 (display surface) when novoltage is applied to the liquid crystal layer 1, and start to tilt fromthe normal direction of the substrates 4 and 5 upon application of thevoltage, thereby effecting the polarization converting function to thelight passing through the liquid crystal layer 1 in the normal directionthereof.

The difference between the liquid crystal display of the presentembodiment and the counterpart using the alignment films 2 and 3 thatalign the liquid crystal in parallel with the substrates is that, in theliquid crystal display of the present embodiment, the liquid crystal isaligned in the normal direction of the substrates 4 and 5, up to andincluding a layer at the interface between the liquid crystal layer 1and electrode substrate, even without applying a voltage. To exploitthese characteristics effectively, the NB (Normally Black) mode, inwhich the black display is shown when no voltage is applied, is used forthe liquid crystal display of the present embodiment. To be morespecific, the display is shown in the reflection display section 9 byallowing circularly polarized light to go into the liquid crystal layer1. In the transmission display section 10, circularly polarized light isalso allowed to go into the liquid crystal layer 1. Circularly polarizedlight is also used in the transmission display section 10 because thephase difference compensation plate 16 (which is also used in reflectiondisplay) affects the polarization of the light exiting the liquidcrystal layer 1, and in consideration of the fact that, in order to useelectrically connected electrodes to drive the liquid crystal layer 1 inboth the reflection display section 9 and transmission display section10, and in order to realize dark display in both sectionssimultaneously, the liquid crystal layer 1 is aligned perpendicular tothe substrates 4 and 5 in the transmission display section as well.Thus, with a combination of the polarization plates 14 and 15 and phasedifference compensation plates 16 and 17, of all the phase differencecompensation plates forming the phase difference compensation plate 17,the retardation of the one closest to the liquid crystal layer 1 is setto 135 nm. Consequently, the liquid crystal display of the presentembodiment can realize satisfactory NB display.

Next, the setting of the liquid crystal layer 1 so as to realizesatisfactory light display in the above combination of the polarizationplates 14 and 15 and the phase difference compensation plates 16 and 17will be explained.

As has been described above, in the present embodiment, the directorconfiguration of the liquid crystal layer 1 starts to tilt from thenormal direction of the substrates 4 and 5 upon voltage application.While the voltage is fully applied to the liquid crystal layer 1, it ispreferable that the liquid crystal layer 1 functions to convert thecircularly polarized light to the linearly polarized light in thereflection display section 9, and to convert the circularly polarizedlight to another circularly polarized light rotating in the reversedirection in the transmission display section 10. When the liquidcrystal layer 1 effects the above converting function, satisfactorylight display can be realized.

To allow the liquid crystal layer 1 to effect the above convertingfunction, for example, it is preferable that the alignment treatment isapplied to the alignment films 2 and 3 in such a manner not to twist theliquid crystal, and that no chiral dopant is added to the liquid crystalcomposition. To be more specific, it is preferable that, when means thewavelength of incident light, retardation of the liquid crystal layervaries by /4 in the reflection display section 9 and by /2 in thetransmission display section 10 upon voltage application.

In case that the thicknesses of the liquid crystal layer 1 are differentin the refection display section 9 and transmission display section 10,the liquid crystal layer 1 can be readily set in the above-describedmanner to effect the above converting function.

In the following, the liquid crystal display of the present embodimentwill be explained by way of examples for purposes of explanation only,without any intention as a definition of the limits of the invention.

Example 11

In the present example, a liquid crystal cell for filling havingdifferent thicknesses of the liquid crystal layer in the reflectiondisplay section 9 and transmission display section 10 is produced in thesame manner as Example 1. Here, vertical aligning alignment films whichalign the liquid crystal perpendicular to the substrates 4 and 5 areused as the alignment films 2 and 3. The alignment treatment is appliedto the alignment films 2 and 3 by means of rubbing, so that the liquidcrystal is aligned slightly tilted with respect to the normalorientation (perpendicular direction) of the substrates 4 and 5.

Note that, however, the thicknesses (d) of the liquid crystal layer areset to 3 m and 6 m in the reflection display section 9 and transmissiondisplay section 10, respectively, and the liquid crystal layer 1 is madefrom a liquid crystal material, that is, liquid crystal having adifference of refractive index (n) of 0.06 and negative dielectricconstant anisotropy. Then, the liquid crystal display is assembled bylaminating the phase difference compensation plates 16 and 17 and thepolarization plates 14 and 15 to the outside of the respective electrodesubstrates of the above liquid crystal cell. Herein, each of the phasedifference compensation plates 16 and 17 is composed of two phasedifference compensation plates.

The optical of the polarization plates 14 and 15, phase differencecompensation plates 16 and 17, and the liquid crystal layer 1 (that is,the lamination orientation of the polarization plates 14 and 15, andphase difference compensation plates 16 and 17, and the alignmentorientation of the liquid crystal) in the reflection display section 9and transmission display section 10 in the liquid crystal display of thepresent example is set forth in Table 6 below for ready comparison withreference to a common orientation.

The optical shown in Table 6 is the position of each optical element onthe display surface when the viewer observes the display surface, andwhen the phase difference compensation plate 16 or 17 is composed ofmore than one phase difference compensation plate, each phase differencecompensation plate forming the phase difference compensation plate 16 or17 is set forth in accordance with the actual position from the viewer'sside. Also, in Table 6, each direction is expressed in degrees from thereference direction set arbitrarily on the display surface, and theretardation of each phase difference compensation plate is expressed innm with respect to a beam of monochrome light having the wavelength of550 nm.

TABLE 6 EXAMPLE 11 SEC. 9 SEC. 10 PLATE 14 TRANSMISSION AXIS 0ORIENTATION (°) PLATE PLATE SLOW AXIS ORIENTATION (°) 15 16 RETARDATION(nm) 270 PLATE SLOW AXIS ORIENTATION (°) 75 RETARDATION (nm) 135 LCLAYER 1 SUBSTRATE 4 −15 −15 ALIGNMENT ORIENTATION (°) SUBSTRATE 5 −15−15 ALIGNMENT ORIENTATION (°) PLATE PLATE SLOW AXIS ORIENTATION (°) −1517 RETARDATION (nm) 135 PLATE SLOW AXIS ORIENTATION (°) −75 RETARDATION(nm) 270 PLATE 15 TRANSMISSION AXIS 90 ORIENTATION (°) SEC. 9: SECTION 9SEC. 10: SECTION 10 PLATES 14 × 15: POLARIZATION PLATES PLATES 16 × 17:PHASE DIFFERENCE COMPENSATION PLATES

The display characteristics of the liquid crystal display of Example 11assembled in the above manner are graphed in FIG. 20. The displaycharacteristics of FIG. 20 were measured in the same manner as Example1, and in the drawing, the horizontal axis represents a root mean squarevalue of the applied voltage and the vertical axis represents thebrightness (reflectance or transmittance).

In FIG. 20, a curve 341 indicates the voltage dependence of thereflectance of the reflection display section 9, and a curve 342indicates the voltage dependence of the transmittance of thetransmission display section 10 in the liquid crystal display of Example11.

As can be understood from FIG. 20, the liquid crystal display of Example11 shows the dark display when no voltage is applied, and it can realizethe display in the so-called normally black (NB) mode, in which thereflectance and transmittance increase with an increasing appliedvoltage. In the present liquid crystal display, not only can thecontrast ratio be set to substantially the same value in the reflectiondisplay section 9 and transmission display section 10, but also thereflection display section 9 and transmission display section 10 showeither the dark or light display simultaneously, thereby realizing thedisplay with excellent visibility.

As has been explained, according to the present embodiment, it isconfirmed that a liquid crystal display of the transflective type canshow satisfactory display both in the reflection display section 9 andtransmission display section 10, if alignment means (vertical aligningalignment film) that aligns the liquid crystal perpendicular to thesubstrate surface touching the liquid crystal (liquid crystal layer 1)is provided to at least one of the reflection display section 9 andtransmission display section 10 in the liquid crystal display of thepresent invention, in which different director configurations of theliquid crystal are realized in the reflection display section 9 andtransmission display section 10 simultaneously.

Embodiment 6

Explained in the present embodiment is a liquid crystal display whichshows the display by changing the alignment orientation of the liquidcrystal in response to a varying voltage while keeping the directorconfiguration of the liquid crystal in parallel with the display surface(substrate) in at least one of the reflecting display section 9 andtransmission display section 10. In other words, in the liquid crystaldisplay of the present embodiment, the liquid crystal molecules start torotate in parallel with the display surface (substrate) upon voltageapplication in at least one of the reflection display section andtransmission display section.

In the following, the liquid crystal display of the present embodimentwill be explained by way of examples for purposes of explanation only,without any intention as a definition of the limits of the invention.Hereinafter, like components are labeled with like reference numeralswith respect to Embodiments 1 through 5, and, for ease of explanation,the description of these components is not repeated here.

Example 12

Explained in the present example with reference to FIGS. 21( a) and21(b) is a liquid crystal display furnished with an optical switchingfunction, in which the liquid crystal molecules are rotated in parallelwith the substrate by means of a transverse electric field (in thein-plane direction with respect to the substrate), by adopting the IPS(In-plane Switching) mode, which is used to increase viewing anglecharacteristics in liquid crystal displays of the transmission type, toa liquid crystal display of the transflective type.

Conventionally, the IPS mode has been used for liquid crystal displaysof the transmission type. However, since the director configuration ofthe liquid crystal is not changed sufficiently for the transmissiondisplay on the comb-shaped electrode used in the IPS mode, the directorconfiguration of the liquid crystal on the comb-shaped electrode doesnot contribute to the display, thereby failing to realize satisfactorydisplay. In the present example, however, regions on the comb-shapedline, which could not be used in the conventional IPS system, are usedto realize the reflection display, thereby making it possible to providea liquid crystal display of the transflective type with high lightefficiency.

FIG. 21( a) is a cross section of a major portion of the liquid crystaldisplay of the present example when no voltage is applied, and FIG. 21(b) is a cross section of the major portion of the liquid crystal displayof FIG. 21( a) when a voltage is applied. Both of FIGS. 21( a) and 21(b)are the cross sections when the liquid crystal cell of the presentliquid crystal display is cut at a plane perpendicular to theorientation along which the electrode line (terminal) of the comb-shapedelectrode provided in the liquid crystal cell extends.

In the liquid crystal display shown in FIGS. 21( a) and 21(b), theliquid crystal layer 1 is sandwiched by a light transmitting substrate51 and a substrate 54, which is given light reflecting properties bybeing provided with a light reflecting comb-shaped electrode 53 (displaycontent overwriting means, voltage applying means, alignment mechanism).Further, the phase difference compensation plate 16 and polarizationplate 14 are provided to the outside of the substrate 51 (the oppositeside from the surface facing the substrate 54), and the phase differencecompensation plate 17 and polarization plate 15 are provided to theoutside of the substrate 54 (the opposite side from the surface facingthe substrate 51). Herein, the phase difference compensation plate 16 iscomposed of a single phase difference compensation plate 16, and thephase difference compensation plate 17 is composed of two phasedifference compensation plates.

The liquid crystal display of the present example is also arranged inthe following manner. That is, on the substrate 54 (electrodesubstrate), one of the pair of substrates sandwiching the liquid crystallayer 1, an insulation film 11 (alignment mechanism) is patterned on aglass substrate 52 by spin-coating an insulation photo-sensitive resin,irradiating the UV rays with masking, so as to leave no photo-sensitiveresin in the transmission display section 10, while forming a layer ofthe photo-sensitive resin of a predetermined thickness in the reflectiondisplay section 9. Consequently, the liquid crystal layer 1 is madethinner in the transmission display section 10 than in the reflectiondisplay section 9.

In the liquid crystal display of the present example, the lightreflecting comb-shaped electrode 53 (alignment mechanism) is formed onthe glass substrate 52 to cover the insulation film 11. The comb-shapedelectrode 53 is a reflective pixel electrode serving both as the liquidcrystal driving electrode for driving the liquid crystal layer 1 and thereflection film (reflecting means), and it is made of metal having highlight reflectance.

In the present liquid crystal display, the director configuration ofliquid crystal molecules 1 a is changed by the electric field appliedthereon by the comb-shaped electrode 53 in the transmission displaysection 10. In the reflection display section 9, the liquid crystallayer 1 is driven by the electric field generated by the comb-shapedelectrode 53, and the reflecting function of the comb-shaped electrode53 is used for the display.

In the present example, the line of the comb-shaped electrode 53 is usedas the reflecting means. However, projections and depressions may beprovided to the surface thereof, or a light scattering film may beadditionally formed on a region opposing the comb-shaped electrode 53 atthe outside of the glass substrate 51 to confer light scatteringproperties to the comb-shaped electrode 53.

In the liquid crystal display of FIGS. 21( a) and 21(b), differentpotentials are given to the adjacent comb-shaped electrodes 53 a and 53b, whereby an electric field develops between the comb-shaped electrodes53 a and 53 b. As shown in FIG. 21( b), the transmission display section10 corresponds to a space between the comb-shaped electrodes 53 a and 53b, and the director configuration of the liquid crystal at thisparticular portion is changed drastically by the pair of comb-shapedelectrodes (comb-shaped electrodes 53 a and 53 b) while keeping itsorientation in parallel with the glass substrate 52. In addition, thereflection display section 9 corresponds to a portion directly above thecomb-shaped electrode 53 (comb-shaped electrodes 53 a and 53 b). In thisparticular portion, the director configuration of the liquid crystaldisplay changes not only in the orientation along the plane of the glasssubstrate 52, but also the orientation perpendicular to the glasssubstrate 52. This is because, as shown in FIG. 21( b), the lines ofelectric force (indicated by broken lines in the drawing) extendsubstantially in parallel with the glass substrate 52 in thetransmission display section 10, while in the reflection display section9, the lines of electric force have components which are perpendicularto the glass substrate 52.

The optical of the polarization plates 14 and 15, phase differencecompensation plates 16 and 17, and the liquid crystal layer 1 (that is,the lamination orientation of the polarization plates 14 and 15, andphase difference compensation plates 16 and 17, and the alignmentorientation of the liquid crystal) in the reflection display section 9and transmission display section 10 in the liquid crystal display of thepresent example is set forth in Table 7 below for ready comparison withreference to a common orientation.

The optical shown in Table 7 is the position of each optical element onthe display surface when the viewer observes the display surface, andeach phase difference compensation plate forming the phase differencecompensation plate 17 is set forth in accordance with the actualposition from the viewer's side.

The direction of director of the liquid crystal layer 1 (the alignmentorientation of the major axis of the liquid crystal molecules 1 a) onthe substrate 51 side is identical with the orientation of the rubbingtreatment applied to the surface thereof, and the alignment orientationon the substrate 54 side is identical with the orientation of therubbing treatment applied to the surface thereof. Hereinafter, thealignment orientation of the liquid crystal layer 1 on the substrate 51side is referred to as the substrate 51 alignment orientation, and thedirection of director of the liquid crystal layer 1 on the substrate 54side is referred to as the substrate 54 alignment orientation.

In Table 7 below, each orientation is expressed in degrees from thereference orientation set arbitrarily on the display surface, and theretardation of each phase difference compensation plate is expressed innm with respect to a beam of monochrome light having the wavelength of550 nm.

Here, the direction, along which the electrode line (terminal) of thecomb-shaped electrode 53 extends, forms an angle of 65 with respect tothe reference orientation, and the director configuration of the liquidcrystal molecules 1 a initially aligned at an angle of 75 both in thereflection display section 9 and transmission display section 10 isre-aligned at a greater angle. In addition, in the present liquidcrystal display, n d of the liquid crystal layer 1 is set to about 130nm in the reflection display section 9 and about 240 nm in thetransmission display section 10.

TABLE 7 EXAMPLE 12 SEC. 9 SEC. 10 PLATE 14 TRANSMISSION AXIS 0ORIENTATION (°) PLATE PLATE SLOW AXIS ORIENTATION (°) 15 16 RETARDATION(nm) 270 LC LAYER 1 SUBSTRATE 51 75 75 ALIGNMENT ORIENTATION (°)SUBSTRATE 54 75 75 ALIGNMENT ORIENTATION (°) PLATE PLATE SLOW AXISORIENTATION (°) −15 17 RETARDATION (nm) 240 PLATE SLOW AXIS ORIENTATION(°) −75 RETARDATION (nm) 270 PLATE 15 TRANSMISSION AXIS 90 ORIENTATION(°) SEC. 9: SECTION 9 SEC. 10: SECTION 10 PLATES 14 × 15: POLARIZATIONPLATES PLATES 16 × 17: PHASE DIFFERENCE COMPENSATION PLATES

In the liquid crystal display set as above, both the reflection displaysection 9 and transmission display section 10 show the dark display whenno voltage is applied to the liquid crystal layer 1. If a voltage isapplied to the liquid crystal layer 1 under these conditions, the liquidcrystal molecules 1 a change their director directions to deviate fromthe orientation (herein, 65 orientation) along which the electrode line(terminal) of the comb-shaped electrode 53 extends. Thus, the presentliquid crystal display can realize the light display by changing thedirector configuration of the liquid crystal with an increasing appliedvoltage.

The display characteristics of the liquid crystal display of Example 12assembled in the above manner are graphed in FIG. 22. The displaycharacteristics of FIG. 22 were measured in the same manner as Example1, and in the drawing, the horizontal axis represents a root mean squarevalue of the applied voltage and the vertical axis represents thebrightness (reflectance or transmittance).

In FIG. 22, a curve 351 indicates the voltage dependence of thereflectance of the reflection display section 9, and a curve 352indicates the voltage dependence of the transmittance of thetransmission display section 10 in the liquid crystal display of Example12. Although the optical characteristics differ in the reflectiondisplay section 9 depending on the position on the comb-shaped electrode53, the optical characteristics of the most typical portion are setforth in FIG. 22.

As can be understood from FIG. 22, the liquid crystal display of Example12 shows the dark display both in the reflection display section 9 andtransmission display section 10 when no voltage is applied, and both thereflectance and transmittance increase with an increasing appliedvoltage. That is, when the applied voltage is 2V, both the reflectanceof the reflection display section 9 and the transmittance of thetransmission display section 10 are 3%, and when the applied voltage isincreased to 5V, both increase to 35% and 38%, respectively. Thus, theabove liquid crystal display can attain satisfactory brightness andcontrast ratio for the light display both in the reflection displaysection 9 and transmission display section 10, thereby realizing thedisplay with excellent visibility. Also, since the contrast ratio ishigher in the transmission display section 10 than in the reflectiondisplay section 9, the above liquid crystal display can further improvethe display quality and show more satisfactory display.

As has been explained, according to Example 12, it was confirmed thatthere can be provided a liquid crystal display of the transflective typewhich can realize the reflection display on the region above thecomb-shaped line 53, which could not be used for the display in theconventional IPS system, while attaining high light utilization.

In the present embodiment, besides the method using the nematic liquidcrystal in the aforementioned IPS mode, a method using the ferroelectricliquid crystal display mode or a method using the anti-ferroelectricliquid crystal display mode can be adopted as a method for realizing theabove-described director configuration of the liquid crystal.

In Example 13 below, a liquid crystal display using the ferroelectricliquid crystal display mode will be explained as another example liquidcrystal display for realizing the above-described director configurationof the liquid crystal.

Example 13

In the present example, a liquid crystal cell is produced in the samemanner as its counterpart used for assembling the liquid crystal displayof Example 1 except that:

surface-stabilized ferroelectric liquid crystal is used as a liquidcrystal material;

the thicknesses (d) of the liquid crystal layer 1 in the transmissiondisplay section 10 and reflection display section 9 are set to 1.4 m and0.7 m, respectively;

n d of the liquid crystal layer 1 in the reflection display section 9and transmission display section 10 are set to 130 nm and 260 nm,respectively; and

a reflective electrode is used for a region corresponding to thereflection display section 9 instead of forming the reflection film 8over the electrode 7 for the reflection display section 9.

To be more specific, the insulation film 11 is patterned over thesubstrate 5 (glass substrate) in such a manner that no photosensitiveresin is left in the transmission display section 10, while a 0.7m-thick layer of the photosensitive resin is formed in the reflectiondisplay section 9. Also, a reflective electrode is formed where theinsulation film 11 is formed (reflection display section 9), and atransparent electrode is formed where the insulation film 11 is notprovided (transmission display section 10). Then, the alignment film 3is formed on the substrate 5 on the surface on which is formed theelectrode, to which the alignment treatment is applied by means ofrubbing, whereby the electrode substrate is produced. The otherelectrode substrate (opposing substrate) placed in an opposing positionto the electrode substrate thus obtained is arranged in the same manneras its counterpart in Example 1. Then, the liquid crystal cell isproduced by filling a space between the two electrode substrates withferroelectric liquid crystal composition containing thesurface-stabilizing ferroelectric liquid crystal. Subsequently, theliquid crystal display is assembled by laminating the phase differencecompensation plates 16 and 17 and the polarization plates 14 and 15 tothe outside of the respective electrode substrates forming the liquidcrystal cell. Herein, the phase difference compensation plate 16 iscomposed of a single phase difference compensation plate, and the phasedifference compensation plate 17 is composed of two phase differencecompensation plates.

The optical of the polarization plates 14 and 15, phase differencecompensation plates 16 and 17, and the liquid crystal layer 1 (that is,the lamination orientation of the polarization plates 14 and 15, andphase difference compensation plates 16 and 17, and the alignmentorientation of the liquid crystal of dark display and light display) inthe liquid crystal display of the present example is set forth in Table8 below for ready comparison with reference to a common orientation.

The optical shown in Table 8 is the position of each optical element onthe display surface when the viewer observes the display surface, andeach phase difference compensation plate forming the phase differencecompensation plate 17 is set forth in accordance with the actualposition from the viewer's side. Also, in Table 8, each orientation isexpressed in degrees from the reference orientation set arbitrarily onthe display surface, and the retardation of each phase differencecompensation plate is expressed in nm with respect to a beam ofmonochrome light having the wavelength of 550 nm.

TABLE 8 EXAMPLE 13 SEC. 9 SEC. 10 PLATE 14 TRANSMISSION AXIS 0ORIENTATION (°) PLATE PLATE SLOW AXIS ORIENTATION (°) 15 16 RETARDATION(nm) 270 LC LAYER 1 SUBSTRATE 51 D: 75 ALIGNMENT ORIENTATION (°) L: 120SUBSTRATE 54 D: 75 ALIGNMENT ORIENTATION (°) L: 120 PLATE PLATE SLOWAXIS ORIENTATION (°) −15 17 RETARDATION (nm) 270 PLATE SLOW AXISORIENTATION (°) −75 RETARDATION (nm) 270 PLATE 15 TRANSMISSION AXIS 90ORIENTATION (°) SEC. 9: SECTION 9 SEC. 10: SECTION 10 D: ORIENTATIONWHEN DARK DISPLAY IS OBSERVED L: ORIENTATION WHEN LIGHT DISPLAY ISOBSERVED PLATES 14 × 15: POLARIZATION PLATES PLATES 16 × 17: PHASEDIFFERENCE COMPENSATION PLATES

The liquid crystal display assembled in the above manner can attainsatisfactory brightness and contrast ratio both in the reflectiondisplay section 9 and transmission display section 10.

As has been explained, any type of liquid crystal display which canrealize different director configurations of the liquid crystal anddifferent thicknesses of the liquid crystal layer in the reflectiondisplay section 9 and transmission display section 10 simultaneously canserve as the liquid crystal display of the transflective type of thepresent invention and show satisfactory display even if the alignmentdirection of the liquid crystal layer 1 changes in the plane of theliquid crystal layer upon the voltage application. In case that theliquid crystal display adopts the IPS mode, the light efficiency can beimproved compared with the conventional liquid crystal display of thetransmission type also adopting the IPS mode. In addition, the liquidcrystal display of the present embodiment can be used in the other modesusing the ferroelectric liquid crystal and the like.

Embodiment 7

In the present embodiment, a specific example of an element substrateand a color filter substrate driven by an active matrix, which realizethe arrangement of the liquid crystal display of the present invention,will be explained.

In assembling the liquid crystal display of the present invention aimingat displaying an image, it is very critical to set a ratio of thetransmission display section and reflection display section based on howfrequently the liquid crystal display is mainly used for thetransmission display and reflection display.

To be more specific, in a first style, like the liquid crystal displayof the transmission type currently used, the transmitted light from thelighting device (back light) serving as the back lighting means ismainly used for the display, and the reflection display section is usedto prevent the wash-out (this style is referred to as thetransmission-main transflective type, hereinafter).

In a second style, the reflection display is mainly used for thedisplay, in which the power-consuming back light is turned ON/OFFfrequently depending on the circumstances to save the power consumption,and therefore, the back light is turned ON only when the ambient lightis so weak that the display content can not be seen by the reflectiondisplay alone (this style is referred to as the reflection-maintransflective type, hereinafter).

The above two styles are distinguished from each other based on whetherthe display is chiefly shown by the transmission display or reflectiondisplay, and for this reason, a specific area ratio of the transmissiondisplay section and reflection display section, a color of the colorfilter in case of color display, etc. must be designed differently ineach style.

Thus, in the first place, a liquid crystal display using for display TFTelements as adopting one of the active matrix methods will be explainedas an example of the liquid crystal display of the transmission-maintransflective type. Hereinafter, like components are labeled with likereference numerals with respect to Embodiments 1 through 6, and, forease of explanation, the description of these components is not repeatedhere.

To begin with, the arrangement of the substrate in the liquid crystaldisplay of the transmission-main transflective type using the TFTelements for the display will be explained with reference to FIGS. 23(a) through 25.

FIG. 23( a) is a plan view illustrating a major portion of the TFTelement substrate for realizing the liquid crystal display of thetransmission-main semi-transmission type of present embodiment. FIG. 23(b) is a view showing a driving electrode 19 for the reflection displaysection 9 (see FIGS. 1, 4, 24, and 25) on the TFT element substrate ofFIG. 23( a). FIG. 23( c) is a view showing a transparent pixel electrode20 on the TFT element substrate of FIG. 23( a).

FIG. 24 is a cross section of the TFT element substrate sliced on lineA-A′ of FIG. 23( a). To be more specific, FIG. 24 is a cross section ofthe TFT element substrate traversing the TFT element 21 to the drivingelectrode 19 and transparent pixel electrode 20 and further to a storagecapacitor section 26. FIG. 25 is a cross section of the TFT elementsubstrate of FIG. 23( a) sliced on line B-B′ of FIG. 23( a), and showsthe arrangement on the cross section at a boundary portion of adjacentpixels.

As shown in FIGS. 23( a), 24, and 25, a pixel electrode 18 driving theliquid crystal layer 1 (see FIGS. 1 and 4) is composed of the drivingelectrode 19 (display content overwriting means, voltage applying means)in the reflection display section 9 and the transparent pixel electrode20 (display content overwriting means, voltage applying means) made ofITO. The driving electrode 19 may be a reflective electrode renderingthe reflecting properties. Also, the driving electrode 19 andtransparent pixel electrode 20 may be electrically connected to eachother when adopting a display method in which the display is notinverted when the displays are shown on the same voltage.

The driving electrode 19 and transparent pixel electrode 20 areconnected to a drain terminal 22 of the TFT element 21 which controls avoltage applied to each pixel for the display. In case that the drivingelectrode 19 is a reflective electrode and furnished with a transmissiondisplay opening 19 a, a region where the transmission display opening 19a is made through is used for the transmission display as thetransmission display section 10.

On the layer beneath the driving electrode 19, the TFT element 21, lines23 and 24, storage capacitor section 26 and a storage capacitor line 27are provided. Note that, however, since these components are made oflight-blocking material, such as metal, the TFT element substrate isproduced in such a manner that none of these components is provided inthe transmission display opening 19 a. In FIG. 23( a), the drivingelectrode 19 is indicated by a two-dot chain line.

Also, as shown in FIG. 24, a major portion of the driving electrode 19of the reflection display section 9 for applying a voltage to thereflection display section 9 forming the driving electrode 18 is spacedapart from the surface of the substrate 19 on which are formed the lines23 and 24 for driving the TFT element 21 and the TFT element 21 (TFTelement substrate surface) by an organic insulation film 25. The organicinsulation film 25 is made of an organic insulation material having alow dielectric constant so as to have a layer thickness of 3 m for thefollowing reasons:

to prevent a parasitic capacitor component, formed between the pixelelectrode 18 and the line 23 which will be used as the gate line of theTFT element 21 or the line 24 which will be used as the source line ofthe TFT element 21, from delaying or deforming a gate signal waveform ora source signal waveform which controls the opening/closing action ofthe TFT element 21, so that a high-resolution dot matrix display isshown; and

to improve the optical characteristics of the reflection display section9 and transmission display section 10 in the liquid crystal display ofthe present embodiment.

The pixel electrode 18 is connected to the drain terminal 22 of the TFTelement 21. The drain terminal 22 is an n⁺ amorphous silicon layer dopedto form the n type semiconductor, and serves as the drain electrode ofthe TFT element 21. In the TFT element substrate of the presentembodiment, the ITO layer placed to touch the drain terminal 22 is usedas the transparent pixel electrode 20, and the driving electrode 19 ofthe reflection display section 9 is formed on the organic insulationfilm 25 which is patterned in such a manner as to cover the transparentpixel electrode 20 partially. In other words, in the liquid crystaldisplay of the transmission-main transflective type using the TFTelement substrate of FIG. 24, the transparent pixel electrode 20 usedfor the transmission display and the driving electrode 19 used for thereflection display are electrically connected at the pattern boundary ofthe organic insulation film 25. Further, smooth protrusion anddepressions may be provided on the surface of the driving electrode 19of the reflection display section 9 as shown in FIGS. 24 and 25 toprevent the surface from turning into a specular reflector.

Also, as shown in FIG. 25, the organic insulation film 25 is formed tocover the line 24 connected to the source terminal 28 of the TFT element21 at the boundary of adjacent pixels on the TFT element substrate,whereby the driving electrode 19 of the reflection display section 9 isformed on the organic insulation film 25.

The TFT element substrate produced in this manner can control theparasitic capacitor component produced by the pixel electrode 18 andlines 23 and 24 through the organic insulation film 25 by setting anappropriate relation between the layer thickness and dielectric constantof the organic insulation film 25. Thus, as shown in FIG. 23( a), thedriving electrode 19 of the reflection display section 9 can be extendeddirectly above the lines 23 and 24. In this case, a space between theadjacent pixel electrodes 18 can be narrowed, and the leaking electricfield from the lines 23 and 24 to the liquid crystal layer 1 throughsuch a space can be reduced. Consequently, the director configuration ofthe liquid crystal layer 1 is hardly disturbed. Thus, the directorconfiguration of the liquid crystal in the liquid crystal layer 1 can becontrolled closer to the boundary between adjacent pixel electrodes 18by setting an adequate relation between the layer thickness anddielectric constant of the organic insulation film 25. Hence, there canbe produced a TFT element substrate for the liquid crystal display ofthe transmission-main transflective type having a high aperture. In thepresent embodiment, the organic insulation film 25 is made of an organicinsulation material having a relative dielectric constant of 3.5 to havea film thickness of 3 m.

As has been explained, in the present embodiment, the TFT elementsubstrate, in which 45% of the entire pixel area is used for thetransmission display, and 38% of the same is used for the reflectiondisplay, is produced. Given that the most general conventional TFTliquid crystal display of the transmission type attains an aperture ofabout 50% in the transmission display section, the present TFT elementsubstrate can be said to be the TFT element substrate for a liquidcrystal display of the transmission-main transflective type with highlight efficiency, because it secures a ratio for the area of thetransmission display section 10 which is substantially the same as inconventional displays, and also shows display by adding the luminance ofthe display light in the reflection display section 9 to thetransmission display light.

The reason why the liquid crystal display of the present embodiment canattain high light utilization is because the light blocking components,such as TFT elements 21, lines 23 and 24, storage capacitor 26, andstorage capacitor line 27, are provided to the reflection displaysection 9, and thus these components do not cause any loss of the lightused for the liquid crystal display.

Next, the color filter substrate placed to oppose the TFT elementsubstrate produced in the above manner will be explained with referenceto FIGS. 26( a) and 26(b).

As shown in FIGS. 26( a) and 26(b), three color filters, namely, a colorfilter 61R for red (R), a color filter 61G for green (G), and a colorfilter 61B for blue (B), are formed on the color filter substrate. Eachof the three color filters 61R, 61G, and 61B is made of photosensitiveresin in which a pigment is dispersed, and formed separately on theglass substrate 62 as a planar and stripe color layer in a matchingposition with the pixels on the TFT element substrate.

Further, as shown in FIG. 26( b), a smoothing layer 501 made oftransparent acrylic resin is formed on the glass substrate 62 on thesurface where the color filters 61R, 61G, and 61B are formed to coverthe same. Also, a 140 nm-thick ITO film is sputtered on the smoothinglayer 501, using a blocking mask covering non-specified portions, toserve as a counter electrode 502 (display content overwriting means,voltage applying means) for the pixel electrode 18 of the TFT elementsubstrate. Consequently, the color filters 61R, 61G, and 61B areseparated from each other by transparent regions.

The superimposing position of the color filter substrate and TFT elementsubstrate is shown in FIG. 26( a). That is, the transmission displayopening 19 a (transmission display section 10) of the driving electrode19 formed in the reflection display section 9 on the TFT elementsubstrate is completely covered with the stripe color filters 61R, 61G,and 61B. On the other hand, only the portion of the driving electrode 19in the reflection display section 9 along the extending direction of thecolor filters 61R, 61G, and 61B is covered with the color filters 61R,61G, and 61B. The transparent regions between adjacent color filters61R, 61G, and 61B are placed to oppose the driving electrode 19 formedin the reflection display section 9 at the other portion (the portionother than the one along extending direction of the color filters 61R,61G, and 61B).

FIG. 27 shows the positions of the reflection display section 9,transmission display section 10, color filters 61R, 61G, and 61B by wayof a combination of the color filter substrate and TFT elementsubstrate. FIG. 27 is a cross section of a major portion of the liquidcrystal display sliced on line C-C′ of FIG. 26( a), that is, the crosssection cut along the line C-C′ of the color filter substrate and TFTelement substrate superimposed for the use of the liquid crystaldisplay.

Thus, any of the color filters 61R, 61G, and 61B is formed in thetransmission display section 10, and the portion of the reflectiondisplay section 9 other than the one along the extending direction ofthe color filters 61R, 61G, and 61B corresponds to the transparentregions among the color filters 61R, 61G, and 61B.

According to the above arrangement, the color filters 61R, 61G, and 61Bof the same kind as those used for the transmission display functiononly on a part of the reflection display section 9. Consequently, thecolor display can be realized in the reflection display, and reflectancenecessary for the refection display section can also be secured.

The transmission colors shown by the light having passed through thecolor filter substrate produced as shown in FIGS. 26( a) and 26(b) maybe the same transmission colors of RGB used for liquid crystal displaysof the transmission type for each of the RGB pixels, or may be adjustedin an adequate manner, as the case may be.

In a combination of the TFT element substrate and color filter substrateshown in FIGS. 26( a) and 27, the transmission display section 10 showsthe display using only the light having passed through the color filters61R, 61G, and 61B, and part of the reflection display section 9 showsthe display using the color filters 61R, 61G, and 61B used for thetransmission display section 10, and the rest shows the display withoutusing the color filters 61R, 61G, and 61B. This is because thereflection display section 9 can not attain sufficient brightness if ituses the color filters 61R, 61G, and 61B entirely, and the brightness iscompensated by providing therein a portion where the color filters 61R,61G, and 61B are not used.

Further, in the present embodiment, since the display light passesthrough the color filters 61R, 61G, and 61B twice in the reflectiondisplay section 9, color filters 61R, 61G, and 61B may be used in thereflection display section 9 which have higher brightness than thoseused in the transmission display section 10.

Also, as in the present embodiment, the color filters 61R, 61G, and 61Bmay be provided at least to the transmission display section 10, and thereflection display section 9 may have a region (portion) where no colorfilters 61R, 61G, and 61B are provided. Further, the color filters 61R,61G, and 61B may be provided to the transmission display section 10alone, and not to the reflection display section 9.

In case that color filters 61R, 61G, and 61B are not provided to thereflection display section 9, a display voltage signal necessary for thetransmission display is a signal suitable for a color display, and adisplay voltage signal necessary for the reflection display is a signalsuitable for a monochrome display. For this reason, there arises adriving problem that the percentage of the contribution of each of theRGB pixels to the brightness is proportional to the luminoustransmittance (Y value) of each color in the transmission displaysection 10, but the percentage in each pixel is the same in thereflection display section 9.

To be more specific, if the display brightness in a case where the Bpixels alone show light display is compared to the display brightness ina case where the G pixels alone show light display, the brightness ineach pixel, in which the luminous transmittance is concerned, varies inthe transmission display section 10 where the color filters 61R, 61G,and 61B are provided, but is the same in the reflection display section9 where the color filters 61R, 61G, and 61B are not provided.

This problem can be eliminated by changing the area of the portion ofthe reflection display section 9 in each of the RGB pixels that does notshow the color display in accordance with the Y value for each of theRGB colors of the color filters 61R, 61G, and 61B used for thetransmission display. Accordingly, the contribution of the monochromedisplay of the reflection display section 9 to the brightness in each ofthe RGB pixels can be adjusted by changing the respective areas of thereflection display section 9 in each RGB pixel and the brightness of themonochrome display based on the area of the reflection display section 9can be reflected in the display luminance of each color.

In addition, the same effect can be obtained by setting the ratio ofcoverage of the reflection display section 9 by the color filter to adifferent value for each color, in the order G, R, B from smallest tolargest. This method has another advantage that the slight greencoloring occurred when a normal polarization plate is used can becompensated. Also, in case that the color filter substrate and TFTelement substrate are superimposed as shown in FIG. 26( a), a relativelylarge allowance can be secured in the accuracy of the superimposingposition. The reason why is because each pixel exists between portionswhere no color filter is formed in the reflection display section 9, ifan area of one of those portions increases by the position shift, theother decreases accordingly.

When the TFT element substrate and color filter substrate described asabove are used, transmission display as good as the transmission displayshown in conventional TFT liquid crystal displays can be displayed withthe use of the lighting device (back light) as the back light means.Further, even when the ambient light is too bright, the display contentcan be seen because the reflected light is used to display the displaycontent very close to the display content in the transmission display.Hence, there can be realized a high-resolution color liquid crystaldisplay which does not cause parallax and does not wash out even whenused with too bright ambient light.

Next, the arrangement of the substrate of the liquid crystal display ofthe reflection-main transflective type will be explained with referenceto FIGS. 28, 29(a) and 29(b). In the liquid crystal display of thistype, the arrangements of the TFT element display and color filtersubstrate are changed, so that it is mainly used as a low powerconsuming liquid crystal display which uses the reflected light of theambient light for the display, and shows the transmission display whenthe ambient light is not sufficiently strong.

FIG. 28 is a plan view showing a major portion of the TFT elementsubstrate for realizing a liquid crystal display of the reflection-maintransflective type of Embodiment 7, and it shows the TFT elementsubstrate which mainly reflects light. In the drawing, the drivingelectrode 19 is represented by a two-dot line.

As shown in FIG. 28, the liquid crystal display of the reflection-maintransflective type is arranged in the same manner as the above liquidcrystal display of the transmission-main transflective type except thatthe transmission display opening 19 a of the driving electrode 19 andthe transparent pixel electrode 20 are made smaller than theirrespective counterparts on the TFT element substrate used in the liquidcrystal display of the transmission-main transflective type.

In other words, in the liquid crystal display of the reflection-maintransflective type, as shown in FIG. 28, the pixel electrode 18 whichdrives the liquid crystal layer 1 (FIGS. 1 and 4) is composed of thedriving electrode 19 and the transparent pixel electrode 20 made of ITOin the reflection display section 9, and the driving electrode 19 andtransparent pixel electrode 20 are connected to the drain terminal 22 ofthe TFT element 21 which controls a voltage applied to each pixel forthe display. Also, the driving electrode 19 is furnished with thetransmission display opening 19 a, and in case that the drivingelectrode 19 is the reflective electrode, a region where thetransmission display opening 19 a is made through is used for thetransmission display as the transmission display section 10 (FIGS. 24,25, and 27).

Also, the TFT element 21, lines 23 and 24, storage capacitor section 26,and storage capacitor line 27 are provided on the layer beneath thedriving electrode 19, and these components are provided outside of thetransmission display opening 19 a.

Note that, however, the TFT element substrate of FIG. 28 is arranged insuch a manner that the transmission display section 10 is smaller andthe reflection display section 9 (FIGS. 24, 25, and 27) is largercompared with those in the TFT element substrate used in the liquidcrystal of the transmission-main transflective type.

In this manner, in the present embodiment, the TFT element substrateusing 13% of the entire pixel area for the transmission display and 70%of the entire pixel area for the reflection display is produced as theTFT element substrate for the liquid crystal display of thereflection-main transflective type.

Compared with the ratio of the transmission display section 10 in theTFT element substrate of the liquid crystal display of thetransmission-main transflective type, 13% is a relatively small valuefor the ratio of the transmission display section 10 in the TFT elementsubstrate for the liquid crystal display of the reflection-maintransflective type. However, in case of the liquid crystal display ofthe reflection-main transflective type using the TFT element substrate,if the transmission display is shown only when the display content cannot be seen with reflection display alone, the ON time of the lightingdevice (back light) as the back light means is controlled. Consequently,the power consumption can be saved, thereby proving of the practical useof the present liquid crystal display.

Next, the following will explain the arrangement of the color filtersubstrate used in a combination with the TFT element substrate withreference to FIGS. 29( a) and 29(b).

As shown in these drawings, the color filter 61R for red (R), colorfilter 61G for green (G), and color filter 61B for blue (B) are providedon the glass substrate 62 in stripes in the same manner as the colorfilter substrate for the liquid crystal display of the transmission-maintransflective type of FIGS. 26( a) and 26(b). A smoothing layer 501 madeof transparent acrylic resin is formed on the glass substrate 62 on thesurface where the color filters 61R, 61G, and 61B are formed to coverthe same. Also, a ITO film is sputtered on the smoothing layer 501,using a blocking mask covering non-specified portions, to serve as acounter electrode 502 for the pixel electrode 18 of the TFT elementsubstrate. Note that, however, the color filter substrate for the liquidcrystal display of the reflection-main transflective type of FIGS. 29(a) and 29(b) is different from the one used for the liquid crystaldisplay of the transmission-main transflective type of FIGS. 26( a) and26(b) in planar shapes and spectral transmittance in each color.

To be more specific, on the color filter substrate of the liquid crystaldisplay of the reflection-main transflective type, the color filters61R, 61G, and 61B (color layer) are formed to cover the reflectiondisplay section 9 on the TFT element substrate entirely, and these colorfilters 61R, 61G, and 61B are made to attain high brightness to allowthe display light to attain satisfactory brightness after having passedthrough the color filters 61R, 61G, and 61B twice, because the displaylight passes through the color filters 61R, 61G, and 61B twice in thereflection display section 9.

For this reason, satisfactory reflection display can be shown in thereflection display section 9 by means of a combination of a TFT elementsubstrate having the reflection display section 9 in a large ratio, anda corresponding color filter substrate suited to reflection display.

Further, in the transmission display section 10, the transmissiondisplay opening 19 a is small, but the display content can also be seenduring the transmission display, which is used only when the ambientlight is not sufficiently strong by suing the lighting device (backlight) as the back lighting means. This is the difference thatdistinguishes the liquid crystal display of the reflection-maintransflective type of the present embodiment from a conventional liquidcrystal display of the reflection type. With the liquid crystal displayof the reflection-main transflective type of the present embodiment,when the transmission display is shown by the color filters 61R, 61G,and 61B adjusted suitably for the reflection display, the chroma is notsatisfactory but the display colors can be confirmed.

Thus, in case that the above liquid crystal display of thereflection-main transflective type shows the color display, it iseffective to use an arrangement whereby the color filters 61R, 61G, and61B are provided to the reflection display section 9 to show the colordisplay, and in the transmission display section 10, either the colorfilters 61R, 61G, and 61B are not provided or color filters 61R, 61G,and 61B having chroma at least as good as the chroma of those providedto the reflection display section 9 are provided partially.

As has been discussed, the liquid crystal display of the reflection-maintransflective type can be arranged in such a manner that the colorfilters 61R, 61G, and 61B are provided at least to the reflectiondisplay section 9, and the transmission display section 10 has a portionwhere the color filters 61R, 61G, and 61B are not provided, or the colorfilters 61R, 61G, and 61B are not provided to the transmission displaysection 10, so that it shows the monochrome display. In the latter case,the transmission display section 10 can be made smaller because thelight transmittance increases. Consequently, a larger area can besecured as the reflection display section 9, and more satisfactorydisplay can be obtained in the normal reflection display.

In this case, like in the liquid crystal display of thetransmission-main transflective type, the area of the portion of thedisplay section where the color display is not shown, that is, the areaof the portion of the transmission display section 10 that does not showthe color display, may be changed for each of the RGB pixels inaccordance with the Y value of each color of the color filters 61R, 61G,and 61B. In other words, each substrate may be produced in such a mannerthat the ratio of the transmission display area for each of the RGBpixels is changed, so that the contribution of monochrome display of thetransmission display section 10 to the brightness in each of the RGBpixels is set adequately by taking the luminous transmittance intoconsideration.

On the other hand, although the power consumption increases for turningON the lighting device (back light) as the back light means, vivid colorfilters suitable for the transmission display in the transmissiondisplay section 10 can be used by brightening the light emanated fromthe lighting device (back light) sufficiently. In this case, not onlythe chroma, but also the color reproduction of the transmitted light canbe secured. In any case, it is very important to keep the lightingdevice (back light) turned OFF as much as possible to save the powerconsumption.

As has been explained, according to the present embodiment, it hasbecome possible to provide a liquid crystal display of thereflection-main transflective type which can save the power consumptionduring normal use, and prevent wash-out in the reflection displaysection 9, while showing the transmission display using the back lightmeans (back light) when occasion demands.

In the above explanation, the TFT element 21 is used as the switchingelement in the active matrix method, and an amorphous silicon TFTelement of the bottom gate type is used as an example of the TFT element21. However, the switching element of the present embodiment is notlimited to the above disclosure, and may be a polysilicon TFT element,or an MIM (Metal Insulator Metal) element known as a 2-terminal element,for example. Also, it should be appreciated that these active elementsare not necessarily used, and can be omitted, as the case may be.

As has been explained, in each liquid crystal display of the presentembodiment, the thickness of the liquid crystal layer can be changed inthe reflection display section 9 and transmission display section 10 bya film thickness of the organic insulation film 25 by employing the TFTelement substrate, in which the driving electrode 19 serving as thedisplay electrode is separated from the lines 23 and 24 by the organicinsulation film 25. Moreover, in each liquid crystal display of thepresent embodiment, even when a thickness of the organic insulation film25 is as thin as 3 m (at which a high capacitor display is allowed basedon the line resistance and parasitic capacitor of the TFT elementsubstrate), a difference in liquid crystal layer thickness sufficient torealize satisfactory display on both the reflection display section 9and transmission display section 10 (as has been discussed Embodiments 1and 2) can be secured.

Thus, a liquid crystal display capable of showing high capacitor displaycan be provided by employing the TFT element substrate arranged in themanner illustrated in FIG. 23( a) or 28 and adopting the liquid crystaldisplay method described in Embodiment 1 or 2.

Further, since the TFT element substrate using the above-mentionedorganic insulation film 25 has been applied in part to the liquidcrystal displays for the transmission display alone adopting the normalTFT element driving method, the above TFT element substrate has fewertechnical problems for the mass production, thereby proving of its highprobabilities for the practical application.

The inventors of the present invention have been carrying out anassiduous study on the production of a reflection film renderingsatisfactory reflection properties by smooth protrusion and depressionsprovided thereon to prevent the display surface from turning into aspecular reflector in the liquid crystal display of the reflection type.They discovered that a similar surface with the protrusion anddepressions can be formed on the organic insulation film 25 used in thepresent invention. Accordingly, the TFT element substrate for the liquidcrystal display of the transmission-main transflective type of FIGS. 23(a) through 27 is furnished with the protrusions and depressions in aportion corresponding to the reflection display section 9.

As has been explained, the present embodiment includes the liquidcrystal display of the transmission-main transflective type and thereflection-main transflective type, and a ratio of the display surfacesof the transmission display section and reflection display section,colors of the color filters in case of color display, etc. are changeddepending on whether the display is mainly shown by the transmissiondisplay or reflection display.

Next, a ratio of the transmission display section and reflection displaysection in the liquid crystal display of the present invention will beexplained in Embodiment 8 below.

Embodiment 8

A ratio between the respective areas of the transmission display sectionand reflection display section must be set by taking the visibility intoconsideration. Stevens et al. (“Brightness Function: Effect ofAdaptation”, Journal of the Optical Society of America, Vol. 53, No. 3,page 375) investigates the brightness perceived visually (perceivedbrightness), giving consideration the adaptation of human vision.According to this publication, even when a human is seeing objects withthe same luminance, the perceived brightness depends on the brightnessto which he is currently adapted, and there has been established aquantitative relation therebetween.

FIG. 30 shows a relation of the adapted brightness for providing theperceived brightness values ranging from 5 brils to 45 brils versus thesample luminance, which was prepared based on the study of Stevens etal. expressed in different units. In the drawing, the horizontal axisrepresents the adapted luminance (unit: cd/m²) to which a viewer of thesample is adapted, and the vertical axis represents the luminance (unit:cd/m²) of the sample (sample luminance) presented to the viewer.

In the drawing, a point A represents the perceived brightness when aviewer adapted to the adapted luminance of 1 cd/m² observes a samplehaving a surface at the luminance of 10 cd/m², and a point B representsthe perceived brightness when a viewer adapted to an adapted luminanceof 1700 cd/m² observes a sample having a surface at the luminance of 300cd/m². FIG. 30 reveals that, given the fact that the perceivedbrightness on both the points A and B shows the same value (9.4 brils),the brightness perceived by human is affected not only by the luminanceof the display surface, but also by the adapted luminance.

Next, the adaptation of the viewer of the display surface of a liquidcrystal display will be discussed.

To begin with, the object to which the viewer adapts will be discussed.When a human observes a particular object and adapts to its brightness,he adapts to the luminance on the surface of the visible object in thevisual surroundings, which generally varies with the circumstantialconditions. However, it is very useful to take the adapted object intoconsideration as a kind of measure, that is, to consider the situationin which the observed object is assumed to be a surface reflecting theambient light. This is because whether indoors or outdoors, a human moreoften adapts to reflection surfaces illuminated by a light source thanto the light-emitting light source itself. In the following, theadaptation of the viewer who adapts one's vision to the object'sreflection surface will be discussed.

In this case, the adapted luminance of FIG. 30 is represented by a valueobtained by multiplying a predetermined value with the illuminance onthe object surface to which the viewer adapts, lighted by anilluminating light source. Let L be the illuminance (unit: lux) and B bethe luminance (unit: cd/m²), then, the luminance (B) on a surface havinga reflectance ratio R in the reference of the perfect reflectingdiffuser surface is computed as: B=LR/. Herein, it is appropriate to usea surface of N5 on Munsell color standard known as having averagereflectance for objects generally observed by humans, and to treat theadapted luminance as the luminance of the surface of the N5 on Munsellcolor standard lighted by predetermined illuminance. In this case, R is0.2.

Further, assume that the illuminance light source lighting the surfaceof N5 on Munsell color standard as the representative of the observedobject also lights the surface of a sample object whose perceivedbrightness is evaluated under the adapted conditions. By the aboveassumption, the perceived brightness of the reflection display sectionwhen the viewer is observing the liquid crystal display can be linked tothe illuminance at which the liquid crystal is lighted through theadapted luminance. Consequently, specific reflectance or ratio of thearea of the reflection display section can be selected based on the dataobtained from the psycho-physical experiments.

As the result of the study of the inventors of the present invention, aspecific standard for perceived brightness can be expressed as thebrightness values set forth in Table 9 below. The inventors reproducedseveral combinations of the adapted luminance and sample luminance, anddiscovered that the brightness expression set forth in Table 9 below isappropriate. Table 9 can be used as the reference when setting thereflection display section based on the perceived brightness.

TABLE 9 PERCEIVED BRIGHTNESS (UNIT: brils)  0£ PB <5 TOO DARK TO SEE  5£PB <10 DARK 10£ PB <20 NORMAL 20£ PB <30 BRIGHT AND GOOD OBSERVATION 30£PB TOO BRIGHT

Here, typical reflectance (R) of the liquid crystal display of thereflection type is about 30% in the polarization plate method. Thus, theoperation of the liquid crystal display of the transflective type of thepresent invention will be explained using the above specific value.

A straight line 601 of FIG. 30 indicates the display operation of theliquid crystal display having the reflectance of 30%. In other words,let L (unit: lux) be the illuminance of the illuminance light sourcelighting the luminance surface to which the viewer adapts, then theadapted luminance by the surface of N5 on Munsell color standard iscomputed as 0.2 L/, because the reflectance (R=20%) of the surface of N5on Munsell color standard varies with the luminance (L/) of the perfectreflecting diffuser surface lighted by the same illuminance lightsource. Likewise, the luminance on the display surface of the liquidcrystal display (sample object) having the reflectance of 30% whenlighted by the same illuminance light source can be computed as: 0.3 L/.In other words, the straight line 601 is obtained by plotting thevarying illuminance (L) on the points which satisfy a relationestablished between the horizontal axis of 0.2 L/ and the vertical axisof 0.3 L/. As in the case of using the liquid crystal display having thereflectance of 30% as the sample object, a straight line 602 is obtainedby plotting the varying illuminance (L) on the points which satisfy arelation established between the horizontal axis of 0.2 L/ and thevertical axis of 0.1 L/.

Next, the usable circumstances of the above liquid crystal displayhaving the reflectance of 30% will be discussed in the following. Theadapted luminance by the surface of N5 on Munsell color standard at theilluminance (about 100,000 lux) of direct sunlight in fair weather,which is the brightest illuminating conditions a human can experience innormal life, is about 6000 cd/m². Here, as shown in FIG. 30, theperceived brightness on the display surface of the liquid crystaldisplay having the reflectance of 30% is the intersection of thestraight line 602 and a straight line 605 indicating the adaptiveluminance of 6000 cd/m², or approximately 30 brils, which is as shown inTable 9 above, is too bright. For this reason, the perceived brightnessat lower illuminance is below the value of the above perceivedbrightness. Hence, the illuminance capable of securing a perceivedbrightness of 10 brils is about 450 lux (found by calculating backwardfrom the corresponding adapted luminance using the above equation). Inother words, when light display having brightness between 10 brils and30 brils inclusive is necessary, the illuminance is 450 lux at theminimum and 100,000 lux at the maximum. Thus, the above liquid crystaldisplay can be used outdoors during normal day time or in interiorshaving illuminance of 450 lux or above (for example, in a room lightedby a light of 450 lux or above), but when used in a darker place, theilluminance is too low to enable the viewer to perceive the display.

A relation of the adapted luminance versus the sample luminance when thereflectance is 50% is shown as a straight line 603 in FIG. 30. As can beunderstood from the straight line 603, when the reflective display isshown at the reflectance of 50% or above as with normal white paper, theperceived brightness exceeds 30 brils under the high illuminancecircumstances of 1800 lux or above (for example, a bright interior nearthe window, or under direct sunlight). Under these circumstances, theviewer feels the white paper is too bright. Thus, it is not appropriateto use the display surface having the reflectance of 50% or above underthe high illuminance circumstance from the standpoint of the visibility,and it can be understood that preferable reflectance of the displaysurface (luminance surface) for the reflection display used under thesecircumstances is 30% or so.

On the other hand, in the reflection display at the reflectance of 30%and the reflection display at the reflectance of 10% respectively shownas the straight lines 601 and 602, the illuminance which can give theperceived brightness of 10 brils is about 450 lux and 3000 lux,respectively. In other words, when the reflectance decreases to onethird, the illuminance 6.7 times brighter is necessary. This means that,if the illuminance is increased because the reflectance of the liquidcrystal display decreases, the eyes of the human adapt to a brightreflective object other than the liquid crystal display, and theillumination must be raised more than the reciprocal of a changing ratioof the reflectance.

Further, as can be understood from FIG. 30, there is a problem that theviewer feels that the display on a display body (for example, a typicaldisplay of the illuminance type) having predetermined luminance is verydark when the surroundings are bright.

However, the liquid crystal display of the transflective type of thepresent invention uses for display a sum of a predetermined luminancedetermined by the back light and the transmittance in the transmissiondisplay section, and an luminance (sample luminance) determined bypredetermined reflectance in the reflection display section. In otherwords, in the liquid crystal display of the transflective type of thepresent invention, the display at the display luminance indicated by acurve 604 in FIG. 30 can be realized, for example. As indicated by thecurve 604, in the liquid crystal display of the transflective type ofthe present invention, the visibility is secured by the reflectiondisplay when the illuminance is high, while the visibility is secured bythe transmission display using the lighting device (back light) as theback light means when the illumination is low.

Next, the perceived brightness was checked when changing the illuminanceusing the surface luminance of the above liquid crystal display of thetransflective type, the result of which is set forth in FIG. 31. Also,relations of the illuminance versus the perceived brightness in theliquid crystal displays of the transmission type and reflectance typeare respectively set forth in FIG. 31 for comparison. Here, theconditions for computing the perceived brightness are: the reflectanceis 30% when the entire display area is used for the reflection displayof color; the transmittance is 7.5% when the entire display area is usedfor the transmission display; the luminance of the back light is 2000cd/m²; the illuminance of the surface to which the viewer is adapted isequal to the illuminance of the display surface of the liquid crystaldisplay of color; and the reflectance of the adapted object surface isassumed to be 20% based on the brightness of N5 on Munsell colorstandard.

In FIG. 31, a value of the perceived brightness when the illuminance isvaried depends on a ratio (Sr) of the reflection display section in thedisplayable area on the liquid crystal display of the transflectivetype. A curve 611 shows a relation of the illuminance versus perceivedbrightness when the normal liquid crystal display of the transmissiontype shows the transmission display alone, that is when Sr=0. Theluminance on the display surface of the liquid crystal display of thetransmission type is 150 cd/m², and when the illuminance is 6000 lux orabove, the perceived brightness is 10 brils or below. Thus, to securethe perceived brightness of 10 brils or above by changing a part of thetransmission display section to the reflection display section, as isindicated by the curve 612, Sr=0.1, that is 1/10 of the displayable areashould be used as the reflection display section.

A curve 613 shows a relation of the illuminance versus the perceivedbrightness of the liquid crystal display of the reflection type whichshows the reflection display alone, that is, Sr=1. The reflectance ofthe display surface on the liquid crystal display of the reflection typeis 30% compared with a perfect reflecting diffuser surface, and when theilluminance is 450 lux or below, the perceived brightness is 10 brils orbelow. Thus, to secure the perceived brightness of 10 brils or above bychanging a part of the reflection display section to the transmissiondisplay section, as is indicated by the curve 614, Sr=0.9, that is, 1/10of the displayable area should be used as the transmission displaysection.

Also, as can be understood from FIG. 31, when Sr is in a range between0.1 and 0.9, satisfactory display with the perceived brightness of 10brils or above and less than 30 brils can be shown. When Sr is set to0.30 (curve 615) or 0.50 (curve 616), satisfactory light display withthe perceived brightness of 20 brils or above and less than 30 brils canbe shown.

Also, surface reflection occurs on the surface of liquid crystaldisplays. The surface reflection interferes with the display moremarkedly as the illuminance of the surrounding rises. In FIG. 31, arelation of the perceived brightness and illuminance caused by thesurface reflection is shown (curve 617). Though the surface reflectionis affected considerably by the finish of the surface, the curve 617shows the relation of the perceived brightness form the surfacerefection versus illuminance in case that the surface reflection causedat the interface between air and a medium having a refractive index of1.5 has the same diffusing abilities as a perfect diffuse surface (thatis, when the reflectance by surface reflection is 4%). Thus, when thesurface reflectance is taken into consideration, in order to obtainsatisfactory display, it is preferable if an area of the reflectiondisplay section accounts for 30% or above (that is, Sr>0.3) of a totalof areas of the reflection display section and transmission displaysection.

According to the above analysis, it is understood that, satisfactorycolor display can be shown both in the reflection display section andtransmission display section of the liquid crystal of the presentembodiment when the area of reflection display section accounts for 30%or above and 90% or below of a total of the areas of the reflectiondisplay section and transmission display section.

A ratio of each display section for showing satisfactory display can beanalyzed in the above manner even when at least one of the reflectiondisplay and transmission display is not used for the color display.However, in any case, the satisfactory display can be realized when aratio of the area of the reflection display section in a total of areasof the reflection display section and transmission display section is inthe above specified range. The liquid crystal displays of thetransmission-main transflective type and the reflection-maintransflective type of Example 7 are assembled using a preferable ratioin the above specified range.

Embodiment 9

In the present embodiment, an active matrix liquid crystal displayadopting the liquid crystal display method described in Embodiments 1and 2, to be more specific, a liquid crystal display for showing thecolor display using the TFT element substrate, will be explained by wayof examples for purposes of explanation only, without any intention as adefinition of the limits of the invention.

A procedure for assembling the active matrix liquid crystal display ofthe present embodiment is composed of a process of producing the TFTelement substrate; a process of producing the color filter substrate; aprocess of producing a liquid crystal cell for filling using the TFTelement substrate and color filter substrate; and a process ofassembling the liquid crystal display by filling the liquid crystal intothe liquid crystal cell for filling obtained in the preceding process.

Thus, the manufacturing method of the active matrix liquid crystaldisplay of each example below in the present embodiment will beexplained from the process of producing the TFT element substrate, tobegin with.

As shown in FIGS. 23( a) through 25, the TFT element substrate iscomposed of a light transmitting substrate 29 on which is formed a TFTelement 21 for each pixel by the following steps.

Here, a glass substrate made of a substance having no alkali contents,such as non-alkali glass, is used as the substrate 29 on which the TFTelements 21 are formed. In the first place, a film of tantalum issputtered on the substrate 29, which will be made into the line 23 asthe gate line and the storage capacitor line 27 by patterning. The line23 and storage capacitor line 27 are patterned in such a manner as tohave gradual step in each (line 23 and storage capacitor line 27), sothat they can be covered satisfactorily with the line 24 formed thereonin the later stage to prevent line disconnection.

Further, a layer of tantalum oxide (Ta₂O₅) is formed over the line 23and storage capacitor line 27 by the anodic oxidation process, overwhich a film of silicon nitride which will serve as a gate insulationfilm is formed. Then, a layer of hydrogenated amorphous silicon as anintrinsic semiconductor layer (i layer) which will be made into aswitching region of the TFT element 21 and a layer of silicon nitride asan etching stopper layer are formed in this order by the CVD (ChemicalVapor Deposition) method using monosilane gas and sputtering (siliconnitride), respectively. Then, the top layer (silicon nitride layer) ispatterned as the etching stopper layer, after which an n⁺ layer, whichwill be made into the source terminal 28 and drain terminal 22 of theTFT element 21, is formed by the CVD method using a monosilane gas mixedwith a phosphine gas. Subsequently, the n⁺ layer and i layer arepatterned, and further, the gate insulation film is patterned. Here,silicon nitride on the connection terminal portion on the line 23 (gateline) outside the display region is removed.

Next, a film of ITO, which will be made into the transparent pixelelectrode 20, is sputtered in such a manner as to touch the sourceterminal 28 and drain terminal 22, and a film of tantalum, which will bemade into the line 24 as the source line, is sputtered. The tantalumfilm is patterned into the line 24, and the ITO film formed beneath thetantalum film is patterned into the transparent pixel electrode 20. Aspreviously mentioned, the transparent pixel electrode 20 is connected tothe source terminal 28 and drain terminal 22, and it also forms ohmiccontact between these terminals (source terminal 28 and drain terminal22) and the lines 23 and 24.

Next, the organic insulation film 25 having the protrusions anddepressions on the surface is formed on the TFT element 21 as theinsulation film of the reflection display section. Then, a film ofaluminum, which will be made into the driving electrode 19 of thereflection display section 9, is sputtered in such a manner as to touchthe transparent pixel electrode 20 at a contact hole formed through theorganic insulation film 25 to serve as the transmission display opening.Subsequently, the aluminum film is patterned by means of the dryetching, whereby the driving electrode 19 serving as the reflectiveelectrode on which are provided the same protrusions and depressions asthose on the surface of the organic insulation film 25 is formed.

In each of the above patterning steps, each component is formed into anecessary shape based on a design, by means of the photolithographictechnique. In the photolithographic steps, the steps of coating anddrying photosensitive resin (resist), irradiating the pattern,developing, baking and curing the resist, dry etching, wet etching,removing the resist, etc. are combined.

The protrusions and depressions are formed in the reflection displaysection 9 by applying an insulation photopolymeric resin materialthereon and subjecting the same successively to the pattern irradiatingstep, developing step, and curing step. In other words, a dot pattern isformed in the developing step, and a smoothing layer is formed on thedot pattern out of the same material. Here, the organic insulation layer25 is not formed in the transmission display section 10.

The TFT element 21 is provided to each pixel in the TFT elementsubstrate produced in the above steps, and each pixel is composed of therefection display section 9 and transmission display section 10. Here,two types of TFT element substrate are produced: the TFT elementsubstrate of FIG. 23( a) and the TFT element substrate of FIG. 28, and aratio of the transmission display section 10 and reflection displaysection 9 in each type is set as described in Embodiment 7.

Next, the procedure of producing the color filter substrate will beexplained. This procedure is composed of a step of producing the RGBcolor layers (color filters) on the substrate, a step of forming asmoothing layer on the color filters, and a step of forming a counterelectrode to the transparent pixel electrode 20 formed on the TFTelement substrate driven by the TFT element 21.

In the present embodiment, as shown in FIG. 26( b) or FIG. 29( b), thecolor filter 61R for red (R), color filter 61G for green (G), and colorfilter 61B for blue (B) are formed on the glass substrate 62 in stripes.Then, a smoothing layer 501 is formed on the glass substrate 62 on thesurface where the color filters 61R, 61G, and 61B are formed to coverthe same, and the counter electrode 502 is formed on the smoothing layer501, whereby the color filter substrate is formed.

During the step of forming the color filter substrate, the color filters61R, 61G, and 61B are formed by using photolithography to pattern aresin material prepared by dispersing the pigment in photosensitiveresin. The method of producing the color filters 61R, 61G, and 61B isnot limited to the above method using the dispersed pigment, and forexample, the electro-deposition method, film transfer method, and dyingprocess can be adopted as well.

The smoothing layer 501 is formed by applying acrylate resin having highlight transmittance on the glass substrate 62 on the surface where thecolor filters 61R, 61G, and 61B are formed, and curing the same by heat.The counter electrode 502 formed on the smoothing layer 501 is a counterelectrode opposing the pixel electrode 18 driven by the TFT element 21,and is formed as a transparent electrode by sputtering layers of ITOwith masking and shaping the resulting deposit of the ITO layers into aplanar shape.

In the present embodiment, two types of color filter substrates areformed: the color filter substrate having high chroma for thetransmission display, and the color filter substrate having highbrightness for the reflection display. The former is patterned as shownin FIGS. 26( a) and 26(b), and the latter is patterned as shown in FIGS.29( a) and 29(b).

Next, the step of producing the liquid crystal cell for filling byplacing the TFT element substrate and color filter substrate to opposeeach other to assemble the liquid crystal layer will be explained.

In this step, alignment films are formed on the TFT element substrateand color filter substrate on their respective opposing surfaces (thesurface where the TFT element 21 is formed on the TFT element substrateand the surface where the color filters 61R, 61G, and 61B are formed onthe color filter substrate) by applying a soluble polyimide solution inthe liquid crystal display area by the offset printing method, andsubjecting the same to the drying and baking steps. Further, thealignment treatment, which determines the alignment direction of theliquid crystal, is applied to these alignment films by means of rubbing.Whether the parallel aligning alignment films or perpendicular aligningfilms are used depends on each example.

Subsequently, spherical spacers of the uniform particle size arescattered on one of the TFT element substrate and color filter substratetreated in the above manner, and a sealing agent for sealing the liquidcrystal layer in a space between the TFT element substrate and colorfilter substrate and fixing these substrates is printed to the othersubstrate. Meanwhile, conductive paste is provided to let the currentflow from the TFT element substrate side to the counter electrode 502 onthe color filter substrate.

Then, the TFT element substrate and color filter substrate are placed tooppose each other with surface provided with the TFT element 21 and thesurface provided with the color filters 61R, 61G, and 61B inside, andafter the positions of these substrates are aligned with respect to eachother, the sealing agent and conductive paste are cured under appliedpressure.

By the above procedure and steps, the mother glass substrate 21containing a plurality of the liquid crystal cells for filling isproduced, and the filling cells are produced by cutting the mother glasssubstrate 21.

Later, the liquid crystal composition is introduced into the liquidcrystal cell by means of vacuum injection, and photopolymeric resin isapplied at the inlet of the liquid crystal and cured throughpolymerization upon irradiation of UV rays, so that the liquid crystallayer filled therein will not be exposed to air, whereby the liquidcrystal cell is produced.

Then, a short-ring portion, provided at the end portion of the TFTelement substrate to short-circuit the line terminals to prevent theelectrostatic breakdown of the TFT element 21, is removed to connect theTFT element 21 to an external circuit for driving the TFT element 21.Further, the back light serving as the light source for the transmissiondisplay is provided, whereby the active matrix liquid crystal display ofthe present embodiment is assembled.

Example 14

The active matrix liquid crystal display of the present example is aliquid crystal display of the transmission-main transflective typeadopting the GH method, which uses for display the same GH method asthat used in the liquid crystal display of Example 1 in Embodiment 1.

The liquid crystal composition used in the present example is preparedin the same manner as Example 1 in Embodiment 1. In other words, theliquid crystal composition using the dichroic dye (dichroic dye 12) usedin Example 1 is used herein too. Also, in the present example, verticalaligning alignment films which align the liquid crystal perpendicular tothe display surface are used, and the alignment treatment is applied tothese alignment films in such a manner as to obtain uniform verticalalignment. In the present example, neither the phase differencecompensation plates nor polarization plates are laminated to the liquidcrystal cell, because the GH method using the dichroic dye as the liquidcrystal composition is adopted.

In the present example, since the transmission display is mainly used,the color filters 61R, 61G, and 61B are designed to have chroma as highas that in the conventional transmission display method, and the colorfilter substrate is placed as shown in FIGS. 26( a) and 26(b). The TFTelement substrate laminated to the color filter substrate has a largetransmission display opening 19 a and a wide transmission displaysection 10, as shown in FIG. 23( a).

As shown in FIGS. 26( a) and 26(b), in the liquid crystal display of thepresent example, only a specific portion of the driving electrode 19 ofthe reflection display section 9 is covered with the color filters 61R,61G, and 61B covering the transmission display opening 19 a which willserve as the transmission display section 10 (a portion opposing thecolor filters 61R, 61G, and 61B in the extending direction thereof). Thedriving electrode 19 also has a display portion which has no colorfilter and thereby transmits white light.

A display signal was inputted into the liquid crystal display assembledin the above manner, and the liquid crystal display was observedvisually. Then, it turned out that, with the liquid crystal display ofthe present example, the back light has to be turned ON. However, withthe back light kept turned ON, the brightness and contrast ratio areboth satisfactory, and satisfactory display is always shown thereon.Further, the display content can be observed visibly under direct light,and there occurs no wash-out.

In other words, in the present example, it has become possible toprovide a high-resolution color liquid crystal display without causingwash-out nor parallax, which can attain high brightness by using theback light when the ambient light is weak, as does the conventionalliquid crystal display, while enabling the user to observe the displaycontent even when the ambient light is strong by changing the brightnessof the reflection display section 9 in proportion to the ambient light.In addition, in the present example, very satisfactory reflectiondisplay having no parallax (double image) can be realized.

Example 15

The active matrix liquid crystal display of the present example is aliquid crystal display of the reflection-main transflective typeadopting the GH method, which uses for display the same GH method asthat used in the liquid crystal display of Example 1 in Embodiment 1.

Like in Example 14, the liquid crystal composition used in the presentexample is prepared in the same manner as Example 1 in Embodiment 1. Inother words, the liquid crystal composition containing the dichroic dye(dichroic dye 12) used in Example 1 is used herein too. Also, in thepresent example, vertical aligning alignment films which align theliquid crystal perpendicular to the display surface are used, and thealignment treatment is applied to these alignment films by means ofrubbing in such a manner as to obtain uniform vertical alignment. In thepresent example, neither the phase difference compensation plates norpolarization plates are laminated to the liquid crystal cell, becausethe GH method using the dichroic dye as the liquid crystal compositionis adopted.

In the present example, since the reflection display is mainly used, thecolor filters 61R, 61G, and 61B are designed to have brightness higherthan that in the conventional liquid crystal display of the transmissiontype, and the color filter substrate is placed as shown in FIGS. 29( a)and 29(b). The TFT element substrate laminated to the color filtersubstrate has a small transmission display opening 19 a and a widereflection display section 9, as shown in FIG. 28.

A display signal was inputted into the liquid crystal display assembledin the above manner, and the liquid crystal display was observedvisually. Then, it turned out that the present liquid crystal displaycan show the reflection display without turning ON the back light whenused during the day time under indoor lighting or surrounding exteriorlight. In the present example, very satisfactory reflection displayhaving no parallax (double image) can be realized. Also, the displaycontent can be visually confirmed by turning ON the back light when theambient light is too weak for the user to observe the display usingreflected light alone.

To be more specific, in the present example, the color filters 61R, 61G,and 61B and the color filter substrate used are designed for thereflection transmission as previously mentioned, and thus the colordisplay can be shown by the reflected light alone. Consequently, thepresent liquid crystal display can be used with the reflection displayalone while keeping the back light turned OFF for the use in indoorlighting or outdoor during the day time. In addition, the visibility canbe secured even when the lighting is too weak by turning ON the backlight, as needed.

Unlike the conventional liquid crystal display of the transmission type,the back light does not have to be kept turned ON in the liquid crystaldisplay of the present embodiment. Consequently, the present liquidcrystal display can save the power consumption while causing no wash-outin the reflection display section 9; moreover, it can show thetransmission display using the back light, as needed.

Example 16

The active matrix liquid crystal display of the present example is aliquid crystal display of the transmission-main transflective type usingthe polarization converting function of the liquid crystal layer for thedisplay, which uses for display the same polarization plate method asused in the liquid crystal display of Example 5 in Embodiment 2.

The liquid crystal composition used in the present example is preparedin the same manner as Example 5 in Embodiment 2. Herein, the phasedifference compensation plates (phase difference compensation plates 16and 17) and polarization plates (polarization plates 14 and 15) arelaminated to the liquid crystal cell (TFT liquid crystal panel) in whichis sealed the liquid crystal. Further, in the present example, thealignment treatment is applied to the parallel aligning alignment filmsby means of rubbing in such a manner as to form the crossed rubbingangle of 250.

Like in Example 14, in the present example, since the transmissiondisplay is mainly used, the color filters 61R, 61G, and 61B are designedto have the same transmission colors as those in the conventionaltransmission display method, and the color filter substrate is placed asshown in FIGS. 26( a) and 26(b). The TFT element substrate laminated tothe color filter substrate has a large transmission display opening 19 aand a wide transmission display section 10 as shown in FIG. 23( a).

As shown in FIGS. 26( a) and 26(b), in the liquid crystal display of thepresent example, only a specific portion of the driving electrode 19 inthe reflection display section 9 is covered with the color filters 61R,61G, and 61B covering the transmission display opening 19 a which willserve as the transmission display section 10 (a portion opposing thecolor filters 61R, 61G, and 61B in the extending direction thereof). Thereflection display section 9 also has a display portion which has nocolor filter and thereby reflects white light.

A display signal was inputted into the liquid crystal display assembledin the above manner, and the liquid crystal display was observedvisually. Then, it turned out that, with the liquid crystal display ofthe present example, the back light has to be kept turned ON. However,with the back light kept turned ON, the brightness and contrast ratioare both satisfactory, and satisfactory display is always shown thereon.Further, the display content can be observed visibly under directsunlight, and there occurs no wash-out.

In other words, in the present example, a liquid crystal displayattaining high brightness by using the back light when the ambient lightis weak, as does the conventional liquid crystal display of thetransmission type is provided, and on the other hand, even when theambient light is strong, the display content can be confirmed visuallyby changing the brightness of the reflection display section 9 inproportion to the ambient light, thereby eliminating the wash-out causedin the conventional display of the illuminance type or liquid crystaldisplay of the transmission type. Further, in the present example, verysatisfactory reflection display having no parallax (double image) can berealized.

Example 17

The active matrix liquid crystal display of the present example is aliquid crystal display of the reflection-main transflective type usingthe polarization converting function of the liquid crystal layer for thedisplay, which uses for display the same polarization plate method asthat used in the liquid crystal display of Example 5 in Embodiment 2.

Like in Example 16, the liquid crystal composition used in the presentexample is prepared in the same manner as Example 5 in Embodiment 2.Herein, the phase difference compensation plates (phase differencecompensation plates 16 and 17) and polarization plates (polarizationplates 14 and 15) are laminated to the liquid crystal cell (TFT liquidcrystal panel) in which is sealed the liquid crystal. Further, in thepresent example, the alignment treatment is applied to the parallelaligning alignment films by means of rubbing in such a manner as to formthe crossed rubbing angle of 250.

Also, like in Example 15, since the reflection display is mainly used,the color filters 61R, 61G, and 61B are designed to have brightnesshigher than that in the conventional liquid crystal display of thetransmission type, and the color filter substrate is placed as shown inFIGS. 29( a) and 29(b). The TFT element substrate laminated to the colorfilter substrate has a small transmission display opening 19 a and awide reflection display section 9 as shown in FIG. 28.

A display signal was inputted into the liquid crystal display assembledin the above manner, and the liquid crystal display was observedvisually. Then, it turned out that the present liquid crystal displaycan show the reflection display without turning ON the back light whenused during the day time under indoor lighting or surrounding exteriorlight. In the present example, very satisfactory reflection displayhaving no parallax (double image) can be realized. Also, the displaycontent can be visually confirmed by turning ON the back light when theambient light is too weak for the user to observe the display usingreflected light alone.

To be more specific, in the present example, the color filters 61R, 61G,and 61B and color filter substrate used are designed for the reflectiondisplay as previously mentioned, and thus the color display can be shownby the reflected light alone. Consequently, the present liquid crystaldisplay can be used with the reflection display alone while keeping theback light turned OFF when used either in indoor lighting or outdoorsduring the day time. In addition, even when the lighting is too weak,the visibility can be secured by turning ON the back light, as needed.

Unlike the conventional liquid crystal display of the transmission type,the back light does not have to be kept turned ON in the liquid crystaldisplay of the present embodiment. Consequently, the present liquidcrystal display can save the power consumption while causing no wash-outin the reflection display section 9; moreover, it can show thetransmission display using the back light, as needed.

As has been discussed by way of Examples 14 through 17, according to thepresent embodiment, a high-resolution active matrix liquid crystaldisplay adopting the liquid crystal display method of Embodiment 1 or 2can be realized.

In Examples 14 through 17, each liquid crystal display is assembled tohave different thicknesses of the liquid crystal layer in the reflectiondisplay section 9 and transmission display section 10 by providing theorganic insulation film 25 (equivalent to insulation film 11) on theactive matrix substrate (TFT element substrate). However, it should beappreciated that the same effect can be attained when any other liquidcrystal display principle of the present invention is adopted.

Embodiment 10

The present embodiment will explain how the luminance of the back lightused in the liquid crystal display of the present invention is changed.

The luminance of the back light is changed mainly for the threefollowing reasons.

A first purpose is to secure the visibility. As has been discussed inEmbodiment 8, the perceived brightness perceived by a human isdetermined by the adapted luminance and the luminance of the displaysurface. Thus, to realize satisfactory display with satisfactoryvisibility, it is effective to change the luminance of the back light tothe perceived brightness of human eyes in response to the adaptedluminance. As described in Embodiment 8, it is preferable to change theluminance of the display surface by controlling the luminance of theback light in response to the adapted luminance, so that the perceivedbrightness is in a range from 10 brils inclusive to 30 brils exclusive.In short, the back light also serves as display surface luminancechanging means. Consequently, the visibility can be improved when thetransmission display is mainly responsible for the display. Here, avalue of the perceived brightness specified in Embodiment 8 is set onthe assumption that the luminance of the display surface is proportionalto the adapted luminance to which the viewer has adapted. Thus,satisfactory display can be obtained only by changing the luminance ofthe back light in accordance with the perceived brightness.

A second purpose is to save the power consumption. There are cases wherethe visibility is not affected much whether the back light is turned ONor OFF. An example of such a case would be when a liquid crystal displayof the transflective type is used where the ambient light lighting theliquid crystal display has sufficiently high illuminance, so that theluminance of the display surface is maintained mainly by the reflectiondisplay section. In this case, the luminance of the display surface maynot be affected even if the luminance of the transmission display ishigh, and in such a case, it is preferable to turn OFF the back light tosave the power consumption.

A third purpose is to furnish more than one function to the liquidcrystal display by enabling the user to switch the color display to themonochrome display and vice versa by turning ON/OFF the back light, incases where the color display is shown by either the reflection displayor transmission display alone.

For example, when the reflection display section is not provided withthe color filters, and shows the monochrome display alone, and thetransmission display section alone is provided with the color filters toshow the color display, the resolution of the reflection display can beset higher than in the transmission display section which displays onemonochrome unit by a plurality of pixels using color filters.Consequently, the reflection display is high-resolution monochromedisplay, while the transmission display is color display with moderateresolution. Conversely, the color filters may be used for the reflectiondisplay alone. In this case, more than one function can be provided tothe liquid crystal display. Consequently, it has become possible tochange the display content significantly in response to the ON/OFF stateby switching the color display to the monochrome display and vice versaor changing the illuminating colors by turning ON/OFF the back light.

As has been discussed above, the luminance of the back light can becontrolled by an adequate signal in response to the intended use or useconditions. When the luminance of the back light is changed in responseto the aforementioned adapted luminance, to improve the visibility, theluminance of the back light is controlled in response to the visualenvironment, such as the illuminance of the light incident on thedisplay surface, and the kinds of the display adopted by the liquidcrystal display.

When the luminance of the back light is controlled in response to theilluminance, it is preferable to control the ON/OFF state of the backlight in the following manner. That is, the back light is turned OFFwhen the illuminance is high, whereas the back light is turned ON in amoderate state when the illuminance is low so as to avoid excessivebrightness, and the back light is turned ON in a strong state when theilluminance is neither too high nor too low.

In this case, if the ON/OFF state of the back light or the luminancethereof are controlled by a signal from external devices or a timerconnected to the liquid crystal cell or liquid crystal display,unnecessary power consumption can be saved.

Further, in controlling the luminance of the back light, if he backlight is only turned ON when the user manipulates the apparatusincluding the liquid crystal display, or for a fixed period thereafter,the overall power consumption of the apparatus can be saved, and theuser can be provided with display he feels to be satisfactory. Theluminance of the back light may also be controlled by any otherapplicable signal besides the illuminance of the light incident on thedisplay surface.

To achieve the above objects, it is very effective to allow the user tocontrol the ON/OFF state of the back light or the luminance thereof, orthe director configuration of the liquid crystal in the reflectiondisplay section and transmission display section by inputting a signalthrough a touch panel (pressed coordinate detecting type input means)layered on the display surface of the liquid crystal cell, or bycontrolling the luminance of the back light in association with someother signal giving a warning to the user. In this manner, a liquidcrystal display with visibility and consuming less power can be providedby controlling the luminance of the display surface from the outside ofthe liquid crystal cell.

Embodiment 11

Explained in the present embodiment is a liquid crystal display of thepresent invention, provided with a touch panel (pressed coordinationdetecting type input means) as information input means, and used in aportable device, which is the field in which the liquid crystal displayof the present invention is chiefly used. Hereinafter, like componentsare labeled with like reference numerals with respect to Embodiments 1through 10, and, for ease of explanation, the description of thesecomponents is not repeated here.

In the present embodiment, a touch panel is attached to the liquidcrystal display of Example 17 in Embodiment 9, whereby a liquid crystaldisplay of the transmission type incorporating an input device isassembled, the arrangement of which is illustrated in FIG. 32. The basicarrangement of the liquid crystal display of the present embodiment,that is, the liquid crystal cell and back light 13, is identical withthe arrangement of Example 17 in Embodiment 9 and Example 5 inEmbodiment 2 except for the touch panel 71, and, for ease ofexplanation, the description of these components is not repeated here.

The touch panel 71 includes a flexible substrate 73 on which is formed atransparent electrode layer 72 and a supporting substrate 75 on which isformed a transparent electrode layer 74. The flexible substrate 73 andsupporting substrate 75 are placed to oppose each other with theirrespective transparent electrode layers 72 and 74 inside, with spacers(not shown) maintaining a predetermined distance therebetween so that,when they are supplied with an electrical current, the transparentelectrode layers 72 and 74 do not touch each other. According to thisarrangement, the transparent electrode layer 72 formed on the flexiblesubstrate 73 and the transparent electrode layer 74 formed on thesupporting substrate 75 keep a space from each other under the normalstate, and are allowed to touch each other at a position only when sucha position on the flexible substrate 73 is specified (pressed) by afinger or a stylus. Accordingly, the touch panel 71 functions as aninput device by detecting a position (coordinate position) where thetransparent electrodes 72 and 74 touch each other by a pressing forceapplied on the flexible substrate 73.

The touch panel 71 is provided between the phase difference compensationplate 16 and substrate 4 of the liquid crystal cell by laminating thephase difference compensation plate 16 and polarization plate 14 on theflexible substrate 73, so that it forms an integral unit together withthe phase difference compensation plate 16 and polarization plate 14. Inthe present embodiment, to attain the effect of the polarization plateof Example 17 by the polarization plate 14 laminated to the touch panel71, both the flexible substrate 73 and supporting substrate 75 formingthe touch panel 71 are made of a material having no birefringence.

In the present embodiment, a space is secured between the supportingsubstrate 75 of the touch panel 71 and the substrate 4 of the liquidcrystal cell, so that the pressure applied on the touch panel 71 is nottransferred to the liquid crystal cell without using a pressure dampingmember, whereby the touch panel 71 and substrate 4 of the liquid crystalcell can attain a pressure transfer preventing effect.

In the liquid crystal display incorporating the input device assembledin the above manner, the back light 13 can be turned OFF when the userdoes not observe the display and turned ON upon input of informationinto the touch panel 71 by changing the luminance of the back light 13in response to signals from the touch panel. Consequently, the liquidcrystal display of the present embodiment can show satisfactory displaywhile saving the power consumption. In addition, according to thepresent embodiment, visibility can be improved by providing thepolarization plate 14, touch panel 71, and liquid crystal cell in thisorder, because the polarization plate 14 also absorbs unwanted reflectedlight from the touch panel 71, thus reducing such unwanted reflectedlight.

As has been explained, a liquid crystal display of the present inventionis arranged in such a manner as to comprise:

a liquid crystal display element having a pair of substrates, to whichalignment members (alignment means), such as alignment films, areprovided to their respective opposing surfaces, and a liquid crystallayer sandwiched by the pair of substrates;

alignment mechanism for providing at least two different directorconfigurations simultaneously on different arbitrary regions used fordisplay in the liquid crystal layer; and

a reflecting member (reflecting means), such as a reflection film or areflective electrode, provided to at least one of the differentarbitrary regions showing different director configurations,

wherein the different arbitrary regions showing different directorconfigurations are used for a reflection display section for showingreflection display and a transmission display section for showingtransmission display, respectively.

According to the above arrangement, the director configuration of theliquid crystal can take different director configurationssimultaneously. Thus, for example, an amplitude of modulation in anopti-physical quantity, such as an amount of absorbed light (absorbance)when a light absorber like a dichroic dye is used for the display, and aphase difference when optical anisotropy is used for the display, can bechanged separately in each region. Thus, according to the abovearrangement, it is possible to obtain transmittance or reflectance basedon an amplitude of modulation in an opti-physical quantity in responseto the director configuration of the liquid crystal layer, therebymaking it possible to set the transmission display section andtransmission display section independently. Hence, according to theabove arrangement, a high contrast ratio can be attained without causingparallax and the visibility can be improved when the surroundings aredark, while satisfactory visibility can be attained even when theambient light is strong. Consequently, according to the abovearrangement, it has become possible to provide a liquid crystal displayof the transflective type, having excellent visibility, and capable ofshowing high-resolution display and using both the reflected light andtransmitted light for the display.

One alignment mechanism which may be suitably used is display contentoverwriting means for overwriting a display content with an evolution oftime. In this case, the display content overwriting means and thealignment mechanism are realized by a single means, so that the aboveliquid crystal display can be obtained without adding any additionalmembers. It should be appreciated that, however, electrical liquidcrystal alignment control means currently used extensively foroverwriting the display content with an evolution of time, namely, anyapplicable means used for voltage application, such as electrodes, canbe used as the display content overwriting means for realizing more thanone state of director configuration of the liquid crystal. In this case,a plurality of regions having different director configurations can beprovided in the liquid crystal layer by using different electrodes inthe transmission display section and reflection display section, orchanging the voltage itself in the transmission display section andreflection display section.

Also, in case that an amplitude of modulation in an opti-physicalquantity, such as an amount of absorbed light and a phase differencecaused by the optical anisotropy, is set independently in the reflectiondisplay section and transmission display section, even if the alignmentdirection of the liquid crystal obtained by the voltage application issubstantially uniform across the region used for the display in theliquid crystal layer, in regions having different thicknesses of theliquid crystal layer, there can be offered the same effect as the oneattained in the case where the alignment direction of the liquid crystallayer is changed. In particular, in the GH method (which uses a lightabsorber like a dichroic dye and makes use of light absorption) or thepolarization plate method which makes use of birefringence orpolarization rotation phenomenon), the phenomena, (such as lightabsorption or birefringence) occurring in the liquid crystal layer, arethe phenomena that take place in association with the light propagation,and thus a relation is established between the distance of the lightpropagation in the liquid crystal layer and the degree of eachphenomenon. Further, the display light passes through the liquid crystallayer twice in the reflection display section and only once in thetransmission display section. Thus, when the director configuration ofthe liquid crystal is substantially the same in the reflection displaysection and transmission display section, neither sufficient brightnessnor contrast ratio can be obtained if the thickness of the liquidcrystal layer is the same in the reflection display section andtransmission display section, thereby making it impossible to eliminatethe above problems.

Therefore, a liquid crystal display of the present invention may bearranged in such a manner as to comprise a liquid crystal displayelement having a pair of substrates, to which alignment means areprovided to their respective opposing surfaces, and a liquid crystallayer sandwiched by the pair of substrates, wherein:

a region used for display in the liquid crystal layer is composed ofregions having at least two different thicknesses of the liquid crystallayer;

the regions having at least two different thicknesses are used for areflection display section and a transmission display section,respectively;

reflecting means is provided at least to the reflection display section;and

the thickness of the liquid crystal layer is thinner in the reflectiondisplay section than in the transmission display section.

According to the above arrangement, it is possible to obtain thetransmittance or reflectance based on an amplitude of modulation in anopti-physical quantity in the regions having different thicknesses ofthe liquid crystal layer, thereby making it possible to set thetransmission display section and transmission display sectionindependently. Hence, according to the above arrangement, a highcontrast ratio can be attained without causing parallax and thevisibility can be improved when the surroundings are dark, whilesatisfactory visibility can be attained even when the ambient light isstrong. Consequently, according to the above arrangement, it has becomepossible to provide a liquid crystal display of the transflective type,having excellent visibility and capable of showing high-resolutiondisplay and using both the reflected light and transmitted light for thedisplay.

The above-arranged liquid crystal display of the present invention maybe arranged in such a manner that, in order to provide at least twodifferent director configurations simultaneously on different arbitraryregions used for display in the liquid crystal layer, an alignment meansis provided in a region of the surface at least one of the substratestouching a region of the liquid crystal layer used for display, so as toimpart at least two different director directions to an directorconfiguration of the liquid crystal layer at an interface touching theregion in which the alignment mechanism is provided.

Besides the above display content overwriting means, an alignment filmprovided on the substrate at the interface touching the liquid crystal,to which the alignment treatment is applied in such a manner as toimpart at least two different directions of director to the directorconfiguration of the liquid crystal layer at the interface touching tothe same, can be used as the means for allowing the directorconfiguration of the liquid crystal to take different directorconfigurations simultaneously. By providing the alignment means in aregion of the surface of the substrate touching the region of the liquidcrystal layer used for display so as to impart at least two differentdirector directions to the director configuration of the liquid crystallayer at the interface touching the region in which the alignment isprovided, the liquid crystal layer can take at least two differentdirector configurations simultaneously upon the voltage application atdifferent arbitrary regions used for the display in the liquid crystallayer, and as a consequence, the reflection display and transmissiondisplay can be shown respectively in these regions having differentdirector configurations in the liquid crystal layer.

In this case, the director configuration of the liquid crystal thatdetermines the optical characteristics and a change of the alignmentupon the voltage application can both be changed by modifying an angleof the director configuration of the liquid crystal layer with respectto the substrate or an orientation angle, thereby allowing each of thereflection display section and transmission display section to showadequate display thereon.

It is preferable that the liquid crystal display of present invention isarranged in such a manner that at least one of the pair of substratesincludes an insulation film at least on the region corresponding to thereflection display section, the insulation film being thicker in theregion corresponding to the reflection display section than in theregion corresponding to the transmission display section.

In other words, it is preferable that the liquid crystal display of thepresent invention is arranged in such a manner that it includes aninsulation film on one of the smooth substrates sandwiching the liquidcrystal layer, and the insulation film is made thinner in a regioncorresponding to the transmission display section than in a regioncorresponding to the reflection display section, or the insulation filmis formed on the region corresponding to the reflection display sectionalone, and not on the region corresponding to the transmission displaysection.

According to the above arrangement, a liquid crystal display having atleast two different thicknesses of the liquid crystal layer in theregion used for the display in the liquid crystal layer (that is, aliquid crystal display having different thicknesses of the liquidcrystal layer in the reflection display section and transmission displaysection) can be readily obtained.

Also, the insulation film not only functions as the liquid crystal layerthickness adjusting means, but also applies a driving voltage to theliquid crystal layer without any loss by forming a display electrode onthe surface touching the liquid crystal layer in the reflection displaysection.

In this case, a light-reflecting film is formed, as reflecting means, onthe substrate placed to oppose the substrate of the display surfaceside, and protrusions and depressions are provided on thelight-reflecting film. This arrangement is effective as specularreflection preventing means for the reflection display which impairsneither the resolution nor display ability of the transmission displaysection. If the insulation film is provided with the protrusions anddepressions like those provided to the light-reflecting film, alight-reflecting film having protrusions and depressions can be readilyformed.

As has been explained, in the liquid crystal display of the presentinvention, the arrangement for providing two different directorconfigurations simultaneously on different arbitrary regions used forthe display in the liquid crystal layer, that is, the alignmentmechanism, is not especially limited as long as it can provide twodifferent director configurations simultaneously on different arbitraryregions used for the display in the liquid crystal display. Examples ofthe alignment mechanism include: electrodes or applied voltages whichprovide different voltages to or generate different electric fields inthe different arbitrary regions used for the display in the liquidcrystal, an alignment film to which the alignment treatment is appliedin at least two different orientations and provided to each of thedifferent arbitrary regions used for the display in the liquid crystaldisplay, an insulation film or substrate formed to have at least twodifferent thicknesses on the regions used for the display in the liquidcrystal layer, particular kinds of liquid crystal materials, a liquidcrystal layer arrangement structured to be driven independently,polarization plates, phase difference compensation plates, or acombination of the aforementioned.

According to the present invention, satisfactory display can be shown onboth the reflection display section and transmission display section bythe aforementioned means and alignment mechanism. However, an optimalratio of the reflection display section to the transmission displaysection for showing satisfactory display varies depending on the desireddisplay, such as color display or monochrome display, or whether thedisplay is shown mainly by the reflection display or transmissiondisplay.

In the liquid crystal display of the present invention, in case thatboth the reflection display section and the transmission display sectionshow color display, it is preferable that an area of the reflectiondisplay section accounts for 30% or above and 90% or less of a total ofareas of the reflection display section and the transmission displaysection.

According to the above arrangement, satisfactory color display can beshown both in the reflection display section and transmission displaysection.

Also, it is preferable that the display content is not inverted in thereflection display section and transmission display section from thestandpoint of the visibility. This is because, if the display content isinverted in the reflection display section and transmission displaysection under the circumstance where the lighting environment changes orsuch a change is hard to predict, a contrast ratio of the displaychanges considerably with the luminance of the ambient light. Such achange in the contrast ratio is deemed as a similar phenomenon to thewash-out in terms of the visibility, thereby deteriorating thevisibility considerably.

Thus, to secure the visibility, it is very important that thetransmission display section and reflection display section show thelight display simultaneously, and the transmission display section andreflection display section show dark display simultaneously.

Thus, the liquid crystal display of the present invention is arranged insuch a manner that when the transmission display section shows the lightdisplay, so does the reflection display section, and when thetransmission display section shows the dark display, so does thereflection display section.

According to the present invention, the reflection display section canshow the light display when the transmission display section does so,and the reflection display section shows the dark display when thetransmission display section does so by changing the alignment mechanismor the thicknesses of the liquid crystal layer. In particular, accordingto the present invention, even if the display content inverts in thereflection display section and transmission display section if nocountermeasure is taken, both the sections readily can show the samekind of display by controlling the overwriting of the display content inthe reflection display section and transmission display sectionindependently by employing the display content overwriting means as thealignment mechanism. Thus, according to the above arrangement, there canbe offered an effect that satisfactory visibility can be secured.

Further, it is preferable that the liquid crystal display of the presentinvention is arranged in such a manner that the liquid crystal layer ismade of liquid crystal composition prepared by blending a dichroic dyewith liquid crystal. If the liquid crystal layer is made of liquidcrystal composition prepared by blending a dichroic dye with liquidcrystal, an amount of absorbed light can be optimized in each of thereflection display section and transmission display section.

It is effective to adopt a method of using the birefringence orpolarization rotation phenomenon using the polarization plate as thedisplay method for showing satisfactory display on both the reflectiondisplay section and transmission display section.

For this reason, it is preferable that a polarization plate is providedto at least one of the pair of substrates on a surface which does nottouch the liquid crystal layer.

According to the above arrangement, since optimal birefringence can beset in each of the reflection display section and transmission displaysection, a satisfactory display can be shown on each. Here, in order torealize sufficient display reliably in the transmission display sectionin a liquid crystal display adopting the polarization plate method inthe reflection display section and having different thicknesses of theliquid crystal layer in the reflection display section and transmissiondisplay section, a polarization plate has to be provided in thetransmission display section on the light incident side in addition tothe one provided on the display surface side.

Also, in the liquid crystal display furnished with the polarizationplate, to switch the display, it is preferable that an amount of changeof the phase difference in the light caused by a change in the alignmentin response to a voltage applied to the liquid crystal layer be setsuitably for the light passing through liquid crystal layer andreturning through the same in the reflection display section, andsuitably for the light passing through the liquid crystal layer in thetransmission display section.

For this reason, it is preferable to arrange the liquid crystal displayof the present invention in such a manner as to further comprise voltageapplying means for applying a voltage to the liquid crystal layer insuch a manner that display light on the reflecting means of thereflection display section has a phase difference of approximately 90between the light display and the dark display, and so that displaylight going out from the liquid crystal layer in the transmissiondisplay section has a phase difference of approximately 180 between thelight display and dark display.

In this case, it is preferable that the liquid crystal layer is alignedwith a twist between the pair of substrates at a twist angle in a rangebetween 60 and 100 inclusive, or in a range between 0 and 40 inclusive.

When the liquid crystal is assembled in such a manner that the liquidcrystal layer is aligned with a twist between the pair of substrates ata twist angle in a range between 60 and 100 inclusive, a change of thealmost rotatory polarized light along the twist of the directorconfiguration of the liquid crystal can be used for the display in theliquid crystal layer in the transmission display section, whereas in therefection display section, a change of the polarized light controlled bythe optical rotatory polarization and retardation can be used for thedisplay.

When the liquid crystal is assembled in such a manner that the liquidcrystal layer is aligned with a twist between the pair of substrates ata twist angle in a range between 0 and 40 inclusive, a change of theretardation can be used for the display in the liquid crystal layer bothin the transmission display section and reflection display section.

Also, in the liquid crystal display of the present invention,satisfactory display can be shown even if the director configuration ofthe liquid crystal is only changed along an in-plane orientationparallel to the substrates.

To be more specific, the liquid crystal display of the present inventionmay be arranged in such a manner that the liquid crystal display elementshows the display by changing the director configuration of the liquidcrystal layer by rotating liquid crystal molecules in parallel with thepair of substrates in at least one of the reflection display section andthe transmission display section.

Further, in the present invention, the drawback of the in-planeswitching method, that is, low light utilization, can be overcome bypositively exploiting for display, as reflection display, theinsufficient director configuration of the liquid crystal that causesthe low transmittance. In other words, the liquid crystal display of thepresent invention may be arranged in such a manner that the liquidcrystal display element includes, in one of the reflection displaysection and transmission display section, voltage applying means forgenerating an electric field in the liquid crystal display along anin-plane direction of the pair of substrates.

The liquid crystal layer may be aligned either in parallel with thedisplay surface like in most of the conventional cases, or perpendicularto the display surface. In other words, the liquid crystal display ofthe present invention may be arranged in such a manner that at least oneof the pair of substrates includes a vertical aligning alignment film ona surface touching the liquid crystal layer at a region corresponding toat least one of the reflection display section and the transmissiondisplay section.

When the vertical aligning alignment film is provided to the substrateand the liquid crystal is aligned perpendicular to the substrates in theabove manner, there can be offered an advantage that a display contrastratio can be improved, which has an advantageous effect in showingsatisfactory display on the liquid crystal display.

In addition, when color display is shown on the liquid crystal displayof the present invention, not only the liquid crystal layer, but alsodesign of the color filter layer is critical, which plays an importantrole in color reproduction. According to the study of the inventors ofthe present invention, the liquid crystal display of the transflectivetype includes two styles.

One is a style that mainly shows the transmission display in general useand uses the reflection display supplementarily, so that the wash-outcan be prevented under the lighting environment where the ambient lightis too strong, and therefore, this style can be used in diversifiedlighting environments compared with displays of the luminous type andliquid crystal displays which show transmission display alone. The otheris a style that mainly shows the reflection display in general use,thereby exploiting the advantage of the reflection display that thepower consumption is small, and turns ON the lighting device known asthe back light under the circumstances where the lighting is too weak,and therefore, like the former style, this style can be also used indiversified lighting environments.

In the former style, (the style showing the transmission displaymainly), by providing a color filter having a transmission color atleast to a region corresponding to the transmission display section in aregion forming the display region of each pixel on one of the pair ofsubstrates, it has become possible to provide a liquid crystal displaywith excellent visibility, capable of showing high-resolution colordisplay while using both the reflected light and transmitted light forthe display.

When the color display is shown in the above manner, it is effective ifthe color filter having a transmission color is provided at least to thetransmission display section in each pixel, and the reflection displaysection either is not provided with a color filter, or is at leastpartially provided with a color filter having the same brightness as thecolor filter provided to the transmission display section, or with acolor filter having a transmission color brighter than that of the colorfilter provided to the transmission display section.

This is because when the color filter used for the transmission displaysection is used for the reflection display section directly, thebrightness becomes insufficient. Thus, when showing the color display inthe reflection display section, the brightness can be compensated byeither forming in the reflection display section a region having nocolor filter, or providing the reflection display section with a colorfilter having a transmission color brighter than the transmission colorof the color filter provided. Consequently, the color display can beshown in the reflection display while securing necessary reflectance forthe reflection display section.

Since the display light passes through the color filter twice in thereflection display section, it is preferable to use a color filterhaving a transmission color brighter than the one in the transmissiondisplay section for the reflection display section.

Also, in the former style mainly using the transmission display, whenthe reflection display section is arranged to have a region where nocolor filter is formed, a display voltage signal necessary for thetransmission display is a signal suitable for the color display, andwhen the color filter is not used at all in the reflection displaysection, a display voltage signal necessary for the transmission displayis a signal suitable for the monochrome display. Thus, in the case whereno color filter is provided in the reflection display section, thepercentage of the contribution of the pixels of respective colors to thebrightness is in proportion to the luminous transmittance in respectivecolors in the transmission display section, but it is equal in thereflection display section. Hence, in the case where no color filter isprovided in the reflection display section, it is preferable to changethe area of the portion of the reflection display section where thecolor display is not shown in accordance with the luminous transmittancein the color of each color filter used for the transmission display.

In the latter style (the style mainly using the reflection display), byproviding a color filter having a transmission color at least to aregion corresponding to the reflection display section in the regionforming the display region of each pixel on at least one of the pair ofsubstrates, it has become possible to provide a liquid crystal displaywith excellent visibility and capable of showing high-resolution colordisplay and using both the reflected light and transmitted light for thedisplay.

When the color display is shown in the above manner, it is effective ifthe color filter having a transmission color is provided at least to thereflection display section in each pixel, and the transmission displaysection either is not provided with a color filter, or is at leastpartially provided with a color filter, having a transmission color withchroma as good as or better than the chroma of the transmission color ofthe color filter provided to the reflection display section.

In this style mainly using the reflection display, when the transmissiondisplay section shows the monochrome display by omitting the colorfilter, the transmission display section can be made smaller because thelight transmittance increases. Accordingly, a larger area can be securedas the reflection display section, and as a consequence, moresatisfactory display can be obtained in the reflection display in thenormal use.

In this style mainly using the reflection display, the contribution ofthe monochrome display in the transmission display section of each pixelto brightness can be set adequately in consideration of the luminoustransmittance by changing the area of the part of the transmissiondisplay section where the color display is not shown, in response to theluminous transmittance in each color of the color filter used for thereflection display.

Also, as has been explained, since the liquid crystal display of thepresent invention has the reflection display section, it renders thecharacteristics of the conventional liquid crystal display of thereflection type, namely, small power consumption. However, if powerconsuming illumination light is kept turned ON, the power consumptionundesirably increases.

Thus, it is preferable to arrange the liquid crystal display of thepresent invention in such a manner as to further comprise a lightingdevice for emitting light to the liquid crystal display element frombehind, the lighting device also serving as display surface luminancechanging means for changing luminance on the display surface.

According to the above arrangement, satisfactory visibility is realizedwhile reducing the power consumption by changing the luminance on thedisplay surface by means of the lighting device.

In this case, it is preferable that the lighting device changes theluminance on the display surface in response to adapted luminance insuch a manner as to attain perceived brightness ranging from 10 brilsinclusive to 30 brils exclusive.

The perceived brightness is determined by the adapted luminance and theluminance on the display surface. Here, to realize satisfactoryvisibility while reducing the power consumption, it is very preferable,if, in changing the brightness of the display surface to attain theforegoing perceived brightness, the lighting device changes its ON/OFFstate or luminance in response to the display content on the liquidcrystal display and the adapted luminance which varies with the visualcircumstances such as the lighting. In particular, in case that thelighting device is controlled from outside the liquid crystal displayelement by pressed coordinate detecting type input means, such as atouch panel, the above effect becomes more noticeable.

In addition, according to the above arrangement, the visibility can beimproved where the transmission display is mainly responsible for thedisplay. Thus, there can be offered an effect that satisfactoryvisibility can be realized with reduced power consumption.

The liquid crystal display of the transflective type of the presentinvention is particularly advantageous in that the pressed coordinatedetecting type input means, such as a touch panel, can be used morereadily compared with liquid crystal displays of the reflection typewhich uses a so-called front light. Hence, to provide a low-powerconsumption liquid crystal display incorporating the input device, it iseffective to realize satisfactory display on the display of thetransflective type using the pressed coordinate detecting type inputmeans.

In other words, it is preferable that the liquid crystal display of thepresent invention further comprises pressed coordinate detecting typeinput means, superimposed on a display surface, which, when pressed,detect a pressed coordinate position.

Further, in case that such pressed coordinate detecting type input meansis used, whether the viewer is using the display or not can be readilydetected by a signal from the pressed coordinate detecting type inputmeans. Thus, to realize satisfactory visibility while reducing the powerconsumption, it is effective to change the luminance on the displaysurface by changing the luminance of the lighting device (which affectsoverall power consumption of the liquid crystal display), or to changethe director configuration of the liquid crystal, in response to theabove signal from the pressed coordinate detecting type input means.

For this reason, it is preferable that the liquid crystal display of thepresent invention further comprises pressed coordinate detecting typeinput means, superimposed on the display surface, which, when pressed,detect a pressed coordinate position, wherein the lighting devicechanges the luminance on the display surface in association with anoutput signal from the pressed coordinate detecting type input means.

Also, it is preferable that the liquid crystal display of the presentinvention further comprises pressed coordinate detecting type inputmeans, superimposed on a display surface, which, when pressed, detect apressed coordinate position, wherein the alignment mechanism changes thedirector configuration of the liquid crystal layer in at least one ofthe reflection display section and the transmission display section inassociation with an output signal from the pressed coordinate detectingtype input means.

Moreover, it is preferable that the liquid crystal display of thepresent invention further comprise pressed coordinate detecting typeinput means, superimposed on a display surface, which, when pressed,detect a pressed coordinate position, and a polarization plate, thepolarization plate, the pressed coordinate detecting type input means,and the liquid crystal display element being provided in that order.

According to the above arrangements, an effect that a low-powerconsumption liquid crystal display incorporating the input device can beprovided, which uses birefringence for the display, and which includes apolarization plate and pressed coordinate detecting type input means. Inaddition, satisfactory visibility can be attained because thepolarization plate also absorbs unwanted reflected light from thepressed coordination detecting type input means.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

1. A liquid crystal display device comprising: a pair of polarizationplates; a pair of substrates interposed between the pair of polarizationplates; and a liquid crystal layer interposed between the pair ofsubstrates, said device including pixels each including a lighttransmitting display section and a light reflecting display section, anda comb-teeth shape electrode being provided on one of the pair ofsubstrates.
 2. The liquid crystal display device of claim 1, wherein aphase difference plate is disposed at least one of (i) between one ofthe pair of polarization plates and corresponding one of the pair ofsubstrates and (ii) between the other one of the pair of polarizationplates and the other one of the pair of substrates.
 3. The liquidcrystal display device of claim 1, wherein two phase difference platesare disposed between the pair of polarization plates, and one of the twophase difference plates is disposed between one of the pair ofpolarization plates and corresponding one of the pair of substrates andthe other one of the two phase difference plates is disposed between theother one of the pair of polarization plates and the other one of thepair of substrates.
 4. The liquid crystal display device of claim 1,wherein both of the light transmitting display section and the lightreflecting display section shows dark display when no voltage isapplied.
 5. The liquid crystal display device of claim 1, wherein astorage capacitor is disposed in the light reflecting display section.6. The liquid crystal display device of claim 1, wherein an alignmentorientation of liquid crystal molecules of the liquid crystal layer ischanged in response to voltage application while the liquid crystalmolecules are kept in parallel to a substrate surface.